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The dilute acid (DA), steam explosion (SE), and a 2-step: steam explosion followed by alkali (SEA) were evaluated for pretreatment of rice husk. The maximum hemicellulose and lignin removal via degradation and dissolution was observed for SEA pretreatment, enabling higher cellulose enrichment (up to 44% w/w) and recovery (up to 78%). The hemicellulose solubilization was >90% for all the pretreatments, while maximum lignin removal (up to 62%) was observed for SEA pretreatment. The particle size in the range of 0.3-0.6 mm enabled higher pretreatment efficiencies in terms of cellulose enrichment. The liquid fraction obtained after DA pretreatment indicated higher COD values (20800-24440 mg/L) as compared to SEA (7800-11400 mg/L) due to lower cellulose recoveries in DAP (54-68%). SEM analysis of the biomass indicated disrupted regions with multiple pores. FTIR analysis revealed cleavage of lignin side chains, and XRD analysis confirmed the increase in cellulose crystallinity post-pretreatment.

Spirulina is known to produce high protein and phycocyanin of commercial importance with concomitant CO2 utilisation. The pH is one of the most important factors for cell growth, CO2 utilisation and controlling contamination. In this study, an indigenously developed automated system for Spirulina cultivation was used at pilot scale, where CO2 supply was aimed to provide carbon source and to control culture pH. Among all the studied pH (7.5 ± 0.1,8.5 ± 0.1, 9.5 ± 0.1), pH 8.5 was found to be the best where biomass productivity, CO2 bio-fixation rate, protein and phycocyanin content were noted as 72 mg L−1 d-1, 0.13 g L-1 d-1, 64%, and 14%, respectively. Though the culture at pH 9.5 experienced late CO2 feeding, it was healthy and showed almost similar metabolite content compared to pH 8.5. The pilot scale automation system developed here can be employed to enhance CO2 fed pH control based performance of Spirulina or any microalgae cultivation.

Chlorella-associated bacteria can have a significant influence on facilitating higher Chlorella biomass yield due to their symbiotic relationship. In this study, non-axenic Chlorella was cultivated in an airlift photobioreactor at high and low-yield conditions. The associated bacterial diversity was analyzed using 16S rRNA metagenome sequencing. At high yield conditions, the bacterial load was observed in the range of 108 -1010 CFU/mL, whereas at low yield conditions, bacteria were more dominant and observed in the range of 1014 -1015 CFU · mL-1 . The majority of the bacterial species associated with Chlorella at high yield conditions belongs to Proteobacteria, Bacteroidetes. Further, Bacteroidetes levels were decreased at low yield conditions and were highly diversified with Planctomycetes, Firmicutes, and 18 others. Predicted functional genes indicated that Chlorella-associated bacteria have the enzymes involved in the metabolism and biosynthesis of B-complex vitamins (i.e., vitamin B12 , thiamin, biotin, pyridoxine, and riboflavin). A critical evaluation revealed that vitamin biosynthesis genes were more abundant at low yield conditions, however, vitamin B12 transport genes (B12 transport ATP binding protein, B12 substrate-binding transportation, B12 permease protein) were less abundant, indicating even though vitamins production occurs, but their availability to Chlorella was limited due to the lack of vitamin transport genes. Further, at high yield, Chlorella-associated bacteria enabled higher growth by supplementing the vitamins. In contrast, at low yield condition - an increased bacterial load, diversity, and limited vitamin transport functional genes affected the Chlorella yield. It can be inferred that Chlorella yield was significantly affected by three factors: associated bacterial load, diversity, and transport functional genes of vitamins.

Lignocellulosic agro-residues can be used as a low-cost raw material for the production of biomethane, which in turn can be used as a sustainable alternative for conventional fossil fuels. In the present study, the effect of mild-thermal pretreatment on the biomethanation potential of two different lignocellulosic substrates, rice straw and napier grass, was evaluated. The substrates were thermally pretreated at 80 °C and 120 °C for 1 h and further subjected to anaerobic digestion at 30 °C for 40 days. The thermally pretreated napier grass showed a methane yield enhancement of 14% (25.66 ml CH4/gsub) with respect to the control, whereas the thermally pretreated rice straw showed an enhancement of 56% (15.12 ml CH4/gsub) with respect to the control. The enhancement in the biomethane yield of the pretreated substrates may be attributed to the partial biodegradation of carbon present in the biomass, which can be validated by the COD reduction observed (up to 67%) after the anaerobic digestion process. FTIR analysis of the substrates indicated the degradation and/or transformation of the organic compounds after thermal pretreatment. In conclusion, the study revealed that mild-thermal pretreatment can be employed as an effective strategy to enhance the biomethanation potential of lignocellulosic substrates.

In the present study, ozone assisted autohydrolysis (OAAH) was evaluated for enhanced generation of xylooligosaccharide (XOS) from wheat bran. The total XOS yield with optimum ozone dose of 3% (OAAH-3) was found to be 8.9% (w/w biomass) at 110 °C in comparison to 7.96% at 170 °C by autohydrolysis (AH) alone. Although, there was no significant difference in oligomeric composition (DP 2–6), significant decrease in degradation products namely furfural (2.78-fold), HMF (3.15-fold), acrylamide (nil) and acetic acid (1.06-fold), was observed with OAAH-3 as a pretreatment option. There was 1-fold higher xylan to XOS conversion and OAAH-hydrolysate had higher DPPH radical scavenging activity than AH. PCA plots indicated clear enhancement in XOS production and lower generation of inhibitors with decrease in treatment temperature. Results of the study therefore suggest OAAH can be an effective pretreatment option that can further be integrated with downstream processing for concentration and purification of XOS.

Life cycle assessment (LCA) of indigenous freshwater microalgae, Scenedesmus dimorphus, cultivation in open raceway pond and its conversion to biodiesel and biogas were carried out. The LCA inventory inputs for the biogas scenario was entirely based on primary data obtained from algal cultivation (in pilot scale raceway pond), harvesting, and biogas production; while only the downstream processing involved in biodiesel production namely drying, reaction and purification were based on secondary data. Overall, eight scenarios were modeled for the integrated process involving: algae-based CO2 capture and downstream processing scenarios for biodiesel and biogas along with impact assessment of nutrient addition and extent of recycling in a life cycle perspective. The LCA results indicated a huge energy deficit and net CO2 negative in terms of CO2 capture for both the biodiesel and biogas scenarios, majorly due to lower algal biomass productivity and higher energy requirements for culture mixing. The sensitivity analysis indicated that variability in the biomass productivity has predominant effect on the primary energy demand and global warming potential (GWP, kg CO2 eq.) followed by specific energy consumption for mixing algal culture. Furthermore, the LCA results indicated that biogas conversion route from microalgae was more energy efficient and sustainable than the biodiesel route. The overall findings of the study suggested that microalgae-mediated CO2 capture and conversion to biodiesel and biogas production can be energy efficient at higher biomass productivity (> 10 g m−2 day−1) and via employing energy-efficient systems for culture mixing (

The effectiveness of O3, O3/Fe2+, and O3/nZVI processes on biomethanated distillery wastewater (BMDWW) was evaluated in terms of biodegradability index (BI) enhancement, biofuel production, COD, color & toxicity reduction. A significant increase in biodegradability, COD, color and toxicity reduction was observed in O3/nZVI compared with O3, O3/Fe2+ due to more hydroxyl radical production. The O3/nZVI pretreated wastewater with enhanced BI (up to 0.71) showed 60% COD removal with additional biogas generation (64% methane content). From the Gas Chromatography Mass Spectrometry (GC-MS) analysis, 18 foremost organic compounds were predominantly detected in the raw distillery wastewater. The disappearance of the corresponding FTIR (Fourier Transform Infrared Spectroscopy) & GC-MS spectra during pretreatment processes signified the degradation or transformation of the recalcitrant present in the distillery wastewater. Subsequent (AnO + AO, AO) of pretreated BMDWW resulted in biodegradation rate enhancement by (1.83, 1.67), (3.5, 2.4) and (4.7, 2.9) times for O3, O3/Fe2+ and O3/nZVI processes respectively.

Composting is a biological process in which the organic matter is degraded by the mixed population of microorganisms in a moist aerobic environment to more stable and humidified end products. The composting process involves an interaction between the organic waste, microorganisms, moisture and oxygen. The molasses-based biomethanated distillery wastewater is presently effectively utilized with sugarcane pressmud through the composting process. The aim of present work was to evaluate the effect of ozone pretreatment on the rate of composting process and the quality of compost obtained. The GC-MS & FTIR analysis of ozone pretreated wastewater indicated the degradation and/or transformation of the organic compounds to simpler compounds present in the wastewater. Composting was performed by mixing fixed weight ratios of pressmud and different ratios of ozone pretreated wastewater (1:3, 1:4 and 1:5). The composting process was found to occur faster in the ozone pretreated wastewater for all the ratios as compared to the untreated wastewater. The final compost characteristics were found to be optimum for the 1:3 and 1:4 ratios of pressmud and wastewater. The bio-oxidative phase duration of composting has been reduced for the ozone pretreated wastewater.

The study reports the biodegradability enhancement of pharmaceutical wastewater along with COD (Chemical Oxygen Demand) color and toxicity removal via O3, O3/Fe2+, O3/nZVI (nano zero valent iron) processes. Nano catalytic ozonation process (O3/nZVI) showed the highest biodegradability (BI = BOD5/COD) enhancement of pharmaceutical wastewater up to 0.63 from 0.18 of control with a COD, color and toxicity removal of 62.3%, 93% and 82% respectively. The disappearance of the corresponding Fourier transform infrared (FTIR) and gas chromatography–mass spectrometry (GC–MS) peaks after pretreatment indicated the degradation or transformation of the refractory organic compounds to more biodegradable organic compounds. The subsequent aerobic degradation study of pretreated pharmaceutical wastewater resulted in biodegradation rate enhancement of 5.31, 2.97, and 1.22 times for O3/nZVI O3/Fe2+ and O3 processes respectively. Seed germination test using spinach (Spinacia oleracea) seeds established the toxicity removal of pretreated pharmaceutical wastewater.

Incorporation of Spirulina in milk as thermally dried powder has the disadvantages of non-uniform distribution with undesirable odor and flavor. Through homogenization (200 ± 10 bar), complete dispersion of fresh Spirulina biomass (7% w/w) in milk was achieved and thereafter a carotenoid enriched probiotic yogurt was developed. Confocal microscopy revealed porous Spirulina-milk protein matrix integrated with smaller fat globules in the yogurt. Spirulina led to a 29.56% increase in Lactobacillus acidophilus count, a 20% reduction in fermentation time and a total probiotic count of 1.2 × 107 CFU mL−1. The protein, total chlorophyll, total carotenoid and β-carotene content (on dry w/w basis) were 3.58 ± 0.08 g 100 g−1, 0.407 ± 0.018 mg g−1, 0.235 ± 0.016 mg g−1 and 13.28 ± 0.08 µg g−1, respectively. During storage (18 days at 6–8 °C), the L. acidophilus count reached 8.83 ± 0.11 log CFU mL−1 with 103.03% increase in the viability by day three and the yogurt retained 71.5% carotenoids. The probiotc Spirulina yogurt was found to be acceptable to consumers as evaluated by affective consumer test.

A comparative life cycle assessment of CO2 capture potential of microalgae, Scenedesmus dimorphus, during autotrophic cultivation in closed airlift photobioreactor and open raceway pond under Indian conditions has been carried out. The LCA inventory inputs for the both the systems were entirely based on primary experimental data obtained by algal cultivation in 1000-L pilot-scale raceway pond and 5-L airlift photobioreactor, respectively. The primary energy demand, environmental impacts and Net CO2 capture efficiency of both the systems were evaluated. The results indicated that the primary energy demand and GWP of airlift photobioreactor were 3.7-fold higher than raceway pond. The NERCO2 (defined as net emission ratio of CO2 and estimated as ratio of CO2 sequestered/CO2 emitted) of raceway pond was fourfold higher as compared to airlift photobioreactor; however, both the cultivation systems were observed to be net negative in terms of CO2 sequestration. However, the process can become net CO2 positive, with up to fourfold and 7.5-fold enhancement in biomass productivities (wrt base value) for raceway pond and airlift photobioreactor, respectively. Further, LCA predictions indicated that utilization of energy-efficient motors with lower specific energy consumptions for microalgae cultivation would facilitate algal cultivation systems to achieve net CO2-positive sequestration.

A biorefinery involves sustainable processing of biomass into a wide variety of bio-based products and bioenergy. During biomass processing for biofuels, many chemicals and enzymes are likely to be used in multi-step processes involving various unit operations and unit processes such as milling, pretreatment, enzymatic hydrolysis, fermentation, and purification. A biorefinery is expected to generate multiple complex wastewater streams characterized by higher chemical oxygen demand along with color, poor biodegradability, inorganic salts, which can pose various challenges during treatment by conventional primary, secondary, and tertiary methods. Further, unlike other industries, the wastewater from biorefineries warrants sustainable energy-efficient treatment processes, preferably with the recovery of the biodegradable portion of chemical oxygen demand (COD) as biogas in order to improve the net energy ratio of the biorefinery. However, the production of biofuels such as biogas and biohydrogen using wastewater from biorefineries is prone to inhibition due to the presence of a number of chemicals that are most likely used in upstream biorefinery operations. This chapter discusses wastewater treatment as an integral part of 1G (molasses-based) and 2G (lignocellulosic residues-based) ethanol biorefineries, with respect to characteristics, conventional treatment options, advanced treatment strategies, and future research needs in view of the emerging stringent regulatory requirements of zero liquid discharge.

Microalgae are sources of high-value metabolites such as lipids, carbohydrates, proteins and pigments. Microalgal metabolites are considered to be sustainable bioproducts with a great significance in food and fuel applications. However, the industrial/large scale production of these metabolites is challenging due to the lack of comprehensive knowledge of metabolic pathways and the aspects of energy conversion. In this chapter we provide an overview of the metabolic pathways involving the biosynthesis of high-value metabolites. Several aspects of metabolism confined exclusively to microalgal species are focused upon. In addition, this chapter also gives a brief description of various strategies for the enhancement of metabolite production.

Chlorella vulgaris is used for food and feed applications due to its nutraceutical, antioxidant and anticancer properties. An airlift photobioreactor comprising transparent draft tube was used for C. vulgaris cultivation. The effect of reactor parameters like hydrodynamics (0.3–1.5 vvm), light intensity (85–400 μmol m(−2) s(−1)), photoperiod (12–24 h) and gas-phase carbon dioxide (CO(2)) concentration (5–15% v/v) were evaluated on microalgae and associated bacterial growth, biochemical profile; with special emphasis on ω-3, ω-6 fatty acids, and vitamin B(12). The optimal growth of C. vulgaris without CO(2) supplementation was observed at 1.2 vvm, which was associated with higher algal productivity, chlorophyll, vitamin B(12) content, and bacterial load along with 72% of nitrate removal. The higher light intensity (400 μmol m(−2) s(−1)) and photoperiod (24:0) increased biomass productivity and ω-3 fatty acid content (in lipid) up to 2–3 fold. The elevated levels of gas-phase CO(2) concentration (15% v/v) enhanced EPA content up to 7% and biomass productivity up to 171 mg L(−1) day(−1). However, the increase in CO(2) concentration lowered vitamin B(12) content (up to 30%) and bacterial load (2–3 log). Also, all the cultivation conditions favoured desirable ω-6/ω-3 ratio(in the range of 1–2). ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13197-019-04118-5) contains supplementary material, which is available to authorized users.

The present study reports the feasibility of ozone oxidation as a pretreatment option for biohydrogen production from complex biomethanated distillery wastewater with complications of low biodegrad...

Coronavirus Disease-2019 (COVID-19), a viral disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was declared a global pandemic by WHO in 2020. In this scenario, SARS-CoV-2 main protease (COVID-19 Mpro), an enzyme mainly involved in viral replication and transcription is identified as a crucial target for drug discovery. Traditionally used medicinal plants contain a large amount of bioactives and pave a new path to develop drugs and medications for COVID-19. The present study was aimed to examine the potential of Emblica officinalis (amla), Phyllanthus niruri Linn. (bhumi amla) and Tinospora cordifolia (giloy) bioactive compounds to inhibit the enzymatic activity of COVID-19 Mpro. In total, 96 bioactive compounds were selected and docked with COVID-19 Mpro and further validated by molecular dynamics study. From the docking and molecular dynamics study, it was revealed that the bioactives namely amritoside, apigenin-6-C-glucosyl7-O-glucoside, pectolinarin and astragalin showed better binding affinities with COVID-19 Mpro. Drug-likeness, ADEMT and bioactivity score prediction of best drug candidates were evaluated by DruLiTo, pkCSM and Molinspiration servers, respectively. Overall, the in silico results confirmed that the validated bioactives could be exploited as promising COVID-19 Mpro inhibitors.

In the present study the life cycle assessment (LCA) of three scenarios for biodiesel production from Scenedesmus dimorphus, a freshwater microalgae, cultivated in open raceway ponds using primary and secondary data was investigated. The main differences in the scenarios were related to biomass productivity, mode of culture mixing and type of energy source. The process steps included algal cultivation in open raceway ponds, harvesting by chemical flocculation, dewatering by mechanical drying option (MDO)/Spray Drying (SD) followed by extraction, reaction, and purification. Supplementation of the cultivation process with electricity derived from defatted algal biomass waste was also analyzed. The scenarios were evaluated for energy demand and environmental impacts amongst the boundary conditions based on a "cradle-to-gate" inventory. The results revealed that among all the scenarios, cultivation in raceway pond was ascertained to be the most energy intensive process with the mode of culture mixing and biomass productivity being the principal determinants. The impacts were found to be directly linked to energy demand and had an inverse relationship with biomass productivity. The geographic location of the energy sources affected the environmental implications of a given process. The integration of defatted algal biomass waste derived electricity with the cultivation system showed a minor reduction in the overall energy demand. (C) 2017 Elsevier B.V. All rights reserved.

The freshwater green algae, Scenedesmus obtusus, was cultivated in a 3.4 L airlift photobioreactor. The hydrodynamic parameters were estimated at different inlet gas flow rates (1, 2, 3, and 4 LPM) and their subsequent impact on the growth and biochemical characteristics of microalgae was studied. The biomass concentration and productivity increased with an increase in flow rates from 1 to 4 LPM. A maximum of 0.07 g L-1 day(-1) productivity of biomass was attained at 3 LPM. An increase of total carbohydrate content from 19.6 to 26.4% was noticed with increment in the inlet flow rate of gas from 1 to 4 LPM. Major variations in total fatty acid content were not observed. The impact of light irradiance on growth and biochemical characteristics of S. obtusus was also evaluated. A maximum biomass productivity of 0.103 g L-1 day(-1) was attained at an illumination of 150 mu mol m(-2) s(-1) under continuous light. The major fatty acids reported were palmitic acid (C16:0), alpha-linolenic acid (C18:3), linoleic acid (C18:2), and oleic acid (C18:1). Biodiesel properties of the microalgae were estimated under various culture conditions. The light profile inside the airlift reactor was experimentally measured and the predictive modelling of light profile was also attempted.

Incorporation of Spirulina in milk as thermally dried powder has the disadvantages of non-uniform distribution with undesirable odor and flavor. Through homogenization (200 ± 10 bar), complete dispersion of fresh Spirulina biomass (7% w/w) in milk was achieved and thereafter a carotenoid enriched probiotic yogurt was developed. Confocal microscopy revealed porous Spirulina-milk protein matrix integrated with smaller fat globules in the yogurt. Spirulina led to a 29.56% increase in Lactobacillus acidophilus count, a 20% reduction in fermentation time and a total probiotic count of 1.2 × 10(7) CFU mL(−1). The protein, total chlorophyll, total carotenoid and β-carotene content (on dry w/w basis) were 3.58 ± 0.08 g 100 g(−1), 0.407 ± 0.018 mg g(−1), 0.235 ± 0.016 mg g(−1) and 13.28 ± 0.08 µg g(−1), respectively. During storage (18 days at 6–8 °C), the L. acidophilus count reached 8.83 ± 0.11 log CFU mL(−1) with 103.03% increase in the viability by day three and the yogurt retained 71.5% carotenoids. The probiotc Spirulina yogurt was found to be acceptable to consumers as evaluated by affective consumer test.

The concomitant generation of renewable energy and material resources with distinct environmental applications for CO2 mitigation and wastewater treatment is one of the hallmarks of microalgal research. Microalgae are photoautotrophic microorganisms with simple growth requirements (light, CO2, N, P, and K) that can synthesize commodity biomolecules (lipids, proteins, and carbohydrates) and high-value metabolites in large amount over a short period of time. Requirement of microalgae for C, N, P, and K is usually met by providing technical grade chemicals which ultimately increases the cost of biomass production. However, since microalgae have the potential to utilize CO2 as well as N, P, and K from wastewater, high-density cultivation of microalgae can be accomplished by utilizing wastewater and CO2.

The present study proposes the selective reduction of the bacterial load in the microalgal cultures without affecting the microalgae. Bacteria was found to be symbiotically associated with microalgae and exponentially increased in the range of 103-1011 CFU/mL during Chlorella cultivation in the airlift photobioreactor. The bacterial load needs to be reduced to meet US-FDA standards (∼103 CFU/mL) for the use of microalgal biomass in food and feed applications. Ozone was evaluated as a non-thermal option for bacterial load reduction of Chlorella cultivated in the airlift photobioreactor. The results of ozonation w.r.t to time (5,10, 15, 20, 25, and 30 min) and dissolved ozone concentrations (0.25, 0.49, 0.75, 0.99 and 1.25 mg of O3/L) showed a significant reduction of bacterial load in the range of 3-6.5log. The bacterial disinfection kinetics of ozonation showed an overall second-order reaction with a rate constant (K) of 0.93 mg-1 min-1 L. Further, confocal laser microscopy imaging of Chlorella and its associated bacterial cells confirmed the selective and significant reduction of associated bacteria. The viability of the Chlorella cells were confirmed with trypan blue viability assay (∼99%) under a fluorescent microscope. The biomass quality with respect to metabolite integrity was also validated wherein no loss was observed. Concluding that ozonation to micoalgal systems could be the potential solution to reduce the bacterial load associated with Chlorella without affecting viability of Chlorella cells.

This work investigated the effect of Fenton, ozone and peroxone pretreatment process on yard waste for biogas production enhancement through breakdown of complex lignocellulosic structure. The pretreatment of yard waste was carried out at different experimental conditions of Fenton (ratio: 1:5, 1:10, 1:20, 1:30, 1:40 and 1: 50; doses; 200 mgL−1: 4000 mgL−1 to 800 mgL−1: 16000 mgL−1; time: 30 min–120 min), ozone (pH: 3, 5, 7 & 9; ozone dosage:0.2 g h−1 to 2.5 g h−1; time: 15 min–60 min), and peroxone (doses: 1 mL to 5 mL) to obtain maximum biogas production. The results indicated that cellulose, hemicellulose and lignin content of yard waste decreased during pretreatment process with increased TRS concentration and in turn improves the biogas production. Pretreatment of yard waste using peroxone process resulted in maximum enhancement of TRS concentration up to 470 mg g−1 biomass from initial value of 55.3 mg g−1 biomass at an optimized condition of ozone dose of 1.8 g h−1 for 30 min with 1 mL H2O2 at pH 3. Subsequently, peroxone pretreatment showed the highest biogas production of 210 mL g−1 VS (63% CH4) as compared to control only 80 mL g−1 VS (35% CH4). The GC-MS and FTIR analysis of pretreated yard waste confirms the degradation of complex lignocellulosic structure.

Ethyl Levulinate (EL), biofuel additive can blend up to 20% with biodiesel to improve its fuel properties. Till the date, there are reports on homogeneous catalysts (H2SO4, ionic liquid) for synthesis of EL from raw biomass like wheat straw. To best of our knowledge, there is no single report on heterogeneous catalyst for one step synthesis of EL directly from wheat straw. This work is a successful attempt to use heterogeneous micro-meso acidic H-USY (post dealumination and desilication) for direct one step conversion of wheat straw to EL with higher EL yield 24.5 wt%, which is probably the highest so far.

In this study, the concentrations of MgSO4, salinity and light intensity were optimised for maximum biomass productivity and lipid content in Chlorella sp. Lipid synthesized at varied experimental conditions was also assessed in detail for biodiesel properties through FAME analysis. FAMEs mainly composed of C16:0, C16:1(9), C16:3(7, 10, 13), C18:0, C18:1(11), C18:2(9, 12), C18:3(9, 12, 15). The optimum biomass productivity (372.50mgL(-1)d(-1)) and lipid content (32.57%) was obtained at MgSO4-150ppm; salinity-12.5ppm, and light intensity-25μmolm(-2)s(-1). However, at this condition the cetane number, a major biodiesel property was not complying with worldwide biodiesel standard. Therefore, further optimisations were done to check the suitability of biodiesel fuel. The optimum biomass productivity (348.47mgL(-1)d(-1)) and lipid content (12.43%) with suitable biodiesel fuel properties was obtained at MgSO4-50ppm, salinity-25ppm and light intensity-100μmolm(-2)s(-1). The validation experiments confirmed the closeness of predicted and measured response values.

In the present study, effects of various cultivation conditions on biomass and lipid productivity, detail FAME signature, CO 2 biofixation and elemental composition of Chlorella sp. and Chlamydomonas sp. have been investigated. In Chlorella sp., N-depletion has enhanced the lipid productivity by 12.70–14.61%. In Chlamydomonas sp., though the lipid content has increased by 22–26% upon N-depletion, lipid productivity has not changed significantly due to concomitant decrease in biomass productivity by 18–25%. The presence of lipid was also confirmed by FTIR spectroscopic analysis of biomass. The characteristic bands observed at 1744.30 cm −1 ( Chlamydomonas sp.) and ( Chlorella sp.) were credited to lipids due to C–O mode of the side chain from ester carbonyl group. Extracted lipid was transesterified to FAMEs. Chlorella sp. at N-replete indoor condition has produced the highest weight percentage of C16:0 (26.64%), C18:0 (3.77%) and C18:1 (27.94%). In Chlamydomonas sp., N-replete indoor condition has resulted in maximum content of MUFA (30.12%), LUFA (53.35%), second highest SFA (29.22%) and DUFA (23.23%). Inverse relationship was observed between MUFA and PUFA at all cultivation conditions. In both the microalgae, C16:0, C18:1 (9), C18:2 (9, 12), C18:3 (9, 12, 15) were identified as the major FAMEs which are suitable to be used as biodiesel components.

Ozone is a strong oxidant and have been effectively used for the degradation and mineralization of organic pollutants. However, the increase in the toxicity and disposal of the recalcitrant organics standalone ozonation process is not effective and sustainable solution for the treatment of industrial wastewater containing recalcitrant. It is therefore necessary to provide a summary of success of hybrid ozonation process for industrial wastewater treatment along with the reaction mechanism for enhancing the molecular ozone reactivity. The paper presents a detailed review of hybrid ozonation process as a combination of two different techniques to enhance the hydroxyl radical formation thereby increasing the process efficiency. An extensive review on the mechanism and application of these hybrid ozonation processes for degradation, mineralization, detoxification of different organic pollutants present in the industrial wastewater is reported.

Thermal assisted alkaline pretreatment (TAAP) of rice husk (RH) was investigated to facilitate enzymatic saccharification by enhancing the enzyme accessibility to cellulosic components. Statistically guided experiments based on the Box-Behnken design involving four factors viz. biomass loading, particle size, NaOH loading and reaction time was considered for optimization. The maximum sugar yield of 371 mg g−1 biomass was obtained at optimized pretreatment condition [biomass loading (10% w/w), particle size (0.25–0.625 mm), NaOH loading (2% w/w), and reaction time (40 min)]. The TAAP of RH resulted in the efficient removal of lignin (14.9–54% (w/w)) with low hemicellulose solubilization [10.7–33.1% (w/w)] and with a simultaneous increase in cellulose concentration [32.65–51.65% (w/w)]. The SEM analysis indicated increased porosity and biomass disruption during TAAP. The FTIR analysis showed progressive removal of noncellulosic constituents, and XRD analysis revealed an increase in cellulose crystallinity post-TAAP indicating the effectiveness of pretreatment.

The study investigates the effect of catalytic ozone pretreatment via Fe2+ and nZVI on biodegradability enhancement of complex textile effluent. The nZVI particles were synthesized and characterized by XRD, TEM and SEM analyses. Results showed that nano catalytic ozone pretreatment led to higher biodegradability index (BOD5/COD = BI) enhancement up to 0.61 (134.6%) along with COD, color and toxicity removal up to 73.5%, 87%, and 92% respectively. The disappearance of the corresponding GC MS & FTIR spectral peaks during catalyzed ozonation process indicated the cleavage of chromophore group and degradation of organic compounds present in the textile effluent. Subsequent aerobic biodegradation of nZVI pretreated textile effluent resulted in maximum COD and color reduction of 78% and 98.5% respectively, whereas the untreated effluent (BI = 0.26) indicated poor COD and color reduction of only 31% and 33% respectively. Bio-kinetic parameters also confirmed the increased rate of bio-oxidation at enhanced BIs. Seed germination test using seeds of Spinach (Spinacia oleracea), indicated the effectiveness of nano catalyzed ozone pretreatment in removing toxicity from contaminated textile effluent.

The treatment of a complex pharmaceutical effluent using a combination of ozonation and biological treatment is reported with the use of ozonation as a pre- and posttreatment. Pretreatment facilitated biodegradability index (BI = BOD/COD) enhancement of up to 0.44 along with COD and color reduction of up to 42% and 33%, respectively. Subsequent anaerobic biodegradation of effluent indicated negligible biogas generation; however, aerobic biodegradation of pretreated effluent resulted in COD reduction (73%) and color reduction (62%), which was also indicated by the biokinetic parameters. Further, ozonation as a posttreatment led to higher overall COD (87%) and color (93%) removal.

The study evaluates the effect of ozone pretreatment on biodegradability enhancement of biomethanated distillery effluent. Results revealed that ozone pretreatment led to biodegradability index (BI = BOD/COD) enhancement up to 0.58 along with COD, color and toxicity reduction of up to 33%, 25% and 40%, respectively. Anaerobic digestion of pretreated effluent resulted in favorable biogas generation with methane content, yield and COD reduction of up to 62%, 39 mL/g COD and 57%, respectively. Kinetics of biogas generation determined by modified Gompertz model indicated methane production potential and production rate of 48.08 mL/g COD and 8.085 mL/g COD.day respectively under optimal conditions.

The present work explores the potential of wet air oxidation (WAO) for pretreatment of mixed lignocel- lulosic biomass to enhance enzymatic convertibility. Rice husk and wheat straw mixture (1:1 mass ratio) was used as a model mixed lignocellulosic biomass. Post-WAO treatment, cellulose recovery in the solid fraction was in the range of 86% to 99%, accompanied by a significant increase in enzymatic hydrolysis of cellulose present in the solid fraction. The highest enzymatic conversion efficiency, 63% (by weight), was achieved for the mixed biomass pretreated at 195 °C, 5 bar, 10 minutes compared to only 19% in the untreated biomass. The pretreatment under the aforesaid con- dition also facilitated 52% lignin removal and 67% hemicellulose solubilization. A statistical design of experiments on WAO process conditions was conducted to understand the effect of process parameters on pretreatment, and the pre- dicted responses were found to be in close agreement with the experimental data. Enzymatic hydrolysis experiments with WAO liquid fraction as diluent showed favorable results with sugar enhancement up to 10.4 g L -1 .

A kinetic study of wet air oxidation pretreatment and induced biodegradability enhancement of a model complex wastewater was studied in the temperature range of 150–200 °C, air pressure 6–12 bar (0.6–1.2 MPa), reaction time 15–120 min and agitation 150–500 rpm. Based on free radical mechanism, a kinetic model is postulated where the electron transfer from air (oxygen) to the substrate was assumed to initiate the free radical generation. According to the model, reaction orders for wet oxidation pretreatment (in terms of COD degradation rate) were found to be 1.0, 0.42 and 0.22 for COD and oxygen partial pressure respectively. The WAO pretreatment led to reorientation and/or breakdown of complex biologically recalcitrant molecules with 3–5-fold increase in biodegradability index. The kinetics of biodegradability index enhancement was successfully correlated with COD degradation kinetics.

In this study, the comparative performance of coagulation, ozone, coagulation + ozone + coagulation and potassium ferrate processes to remove chemical oxygen demand (COD), color, and toxicity from a highly polluted textile wastewater were evaluated. Experimental results showed that ferrate alone had no effect on COD, color and toxicity removal. Whereas, in combination with FeSO4, it has shown the highest removal efficiency of 96.5%, 83% and 75% for respective parameters at the optimal dose of 40 mgL−1 + 3 ml FeSO4 (1 M) in comparison with other processes. A seed germination test using seeds of Spinach (Spinacia oleracea) also indicated that ferrate was more effective in removing toxicity from contaminated textile wastewater. Potassium ferrate also produces less sludge with maximum contaminant removal, thereby making the process more economically feasible. Fourier transform infrared spectroscopy (FTIR) analysis also shows the cleavage of the chromophore group and degradation of textile wastewater during chemical and oxidation treatment processes.

Anthropogenic activities have substantially increased the level of greenhouse gases (GHGs) in the atmosphere and are contributing significantly to the global warming. Carbon dioxide (CO2 ) is one of the major GHGs which plays a key role in the climate change. Various approaches and methodologies are under investigation to address CO2 capture and sequestration worldwide. Carbonic anhydrase (CA) mediated CO2 sequestration is one of the promising options. Therefore, the present review elaborates recent developments in CA, its immobilization and bioreactor methodologies towards CO2 sequestration using the CA enzyme. The promises and challenges associated with the efficient utilization of CA for CO2 sequestration and scale up from flask to lab-scale bioreactor are critically discussed. Finally, the current review also recommends the possible future needs and directions to utilize CA for CO2 sequestration.

Enzymatic hydrolysis and fermentation methods were evaluated on alkaline peroxide pretreated shea tree sawdust conversion to ethanol. Optimum pretreatment conditions of 120 °C reaction temperature, 30 min reaction time, and 20 mL L−1 of water hydrogen peroxide concentration (1%(v/v)H2O2) solubilized 679 g kg−1 of hemicellulose and 172 g kg−1 of lignin. 617 g kg−1 cellulose was retained in the solid fraction. The maximum yield of reducing sugar with optimized enzyme loadings by two enzyme preparations (cellulase and β-glucosidase) was 165 g kg−1 of dry biomass. The ethanol yield was 7.35 g L−1 after 72 h incubation period under the following conditions: 2% cellulose loading, enzyme concentration was 25 FPU (g cellulose)−1 loading, yeast inoculums was 10% (v/v), 32 oC, and pH 4.8. The pretreatments gave information about the hindrances caused by lignin presence in lignocellulosic materials and that hemicelluloses are better hydrolyzed than lignin, thereby enhancing enzymatic digestibility of the sawdust material.

Present study describes the induction of carbonic anhydrase (CA) activity in Chlamydomonas sp. in presence of calcium carbonate. Results indicated that calcium carbonate increased the activity of extracellular CA enzyme by 14-fold compared to culture grown at 3 % CO2, and by fourfold compared to the culture grown at 0.03 % CO2. CA was purified by gel exclusion followed by ion exchange chromatography. Molecular weight of the purified CA was found to be approximately 28 kDa. The enzyme showed optimum stability in the pH range of 8.0–9.0 and temperature of 35 °C. CA activity was inhibited with Hg2+ and Pb2+, while Zn2+ was found to accelerate its activity. Purified CA was employed for carbonation reaction with CO2 and the calcite produced was characterized by scanning electron microscope and X-ray diffraction. The enhancement in CA activity was found to be reliable, convenient, and may be employed for CO2 sequestration using whole cells or immobilized bioreactor systems.

Kinetics of nano-catalysed dark fermentative biohydrogen production from molasses-based distillery wastewater has been reported. Iron oxide nanoparticle was supplemented (10-200 mgL -1 ) to the wastewater to enhance the biohydrogen production. Andrew's inhibition model was employed to evaluate the rate of hydrogen production (R H2 ) and hydrogen yield at different concentration of iron oxide nanoparticles. The maximum R H2 and specific hydrogen yield (SHY) for the fermentative hydrogen production system at different concentration of iron oxide nanoparticle were found to be 80.7 ml/hr and 44.28 ml H 2 /g COD. Michaelis-Menton equation was applied to determine the rate of hydrogen production (R H2 ) and yield of H 2 (SHY) at different initial pH (5, 6 & 7). Andrew's inhibition model has been used to describe the inhibitory effect of substrate concentration on the rate of H2 production (R H2 ). R H2 decreased with the increase in substrate concentration but SHY first decreased with substrate concentration and it is maximum at higher substrate concentration of 110 gL -1 . Monod model has been used to determine the growth kinetic parameters. The values of maximum rates of microbial growth (μ m ) and substrate utilization (R su ) were 0.1 g biomass/g biomass/day and 14.03 g COD/g biomass/day respectively at different iron oxide nanoparticles concentration.

Response surface methodology (RSM) was adopted for the optimization of process variables in the alka- line peroxide oxidation (APO) pretreatment of Vitellaria paradoxa sawdust based on central composite design (CCD) experiments. A 2 3 five level CCD with central and axial points was used to develop a statis- tical model for the optimization of process variables. Maximum response for the pretreatment was obtained when applying the optimum values for temperature (150 C), time (45 min), and 1% (v/v) H2O2. At the optimum conditions, up to 70% of the initial hemicellulose was removed in treatments, which also caused some delignification (up to 11% of the initial lignin was removed), whereas cellulose was almost quantitatively retained in the solid phase. Alkaline peroxide assisted wet air oxidation (APA- WAO) pretreatment at the optimum conditions resulted in enrichment up to 60% cellulose content along with solubilization of 80% hemicellulose and 17% of lignin initially present in the raw sawdust. Reducing sugars yield after 72 h enzymatic hydrolysis of pretreated biomass at optimized APO conditions was 177.89 mg equivalent glucose g � 1 dry biomass. Addition of 10 bar air pressure at the optimized pretreat- ment conditions increased the sugars yield to 263.49 mg equivalent glucose g � 1 dry biomass.

In this study alkaline wet air oxidation (WAO), alkaline peroxide assisted wet air oxidation (APAWAO), and enzymatic hydrolysis methods were evaluated for conversion of wood residue (sawdust) to reducing sugars. Cellulose content, hemicellulose solubilization, and ligninremovalforWAOpretreatmentconditionswereoptimizedbystatisticalanalysisusing a2 3 -full factorial design with reaction temperature, air pressure, and reaction time as the

In recent years, complex industrial wastewater generated from distillery, heterocyclic, pharmaceutical, chemical manufacturing industries, and so on, has become a major area of concern. These complex efuents are characterized by high chemical oxygen demad (COD), color, presence of recalcitrant intermediates and poor biodegradability, which warrant the need for efcient and sustainable processes for their treatment. Conventional biological treatment processes have severe limitations due to the high recalcitrant nature of these efuents, which often results in ineffective treatment. Alternative physicochemical options are capital and energy intensive and also may generate secondary waste streams. The advanced oxidation processes (AOP) such as wet air oxidation (WAO), ozonation, UV, H2O2, and the like, are emerging techniques and have immense potential for effective treatment of complex efuents. AOPs are characterized by generation of hydroxyl radicals that are highly reactive and can easily degrade/alter/modify recalcitrant/toxic contaminants. They are, however, presently beset with problems of high capital and energy intensiveness and are unsustainable as standalone options. The synergistic combination of AOP pretreatment of complex efuent for biodegradability enhancement followed by biological treatment has potential for providing high treatment efciency along with high overall sustainability. Therefore, the primary emphasis of any advanced oxidative pretreatment process should be on partial oxidation/minimal mineralization leading to the formation of biologically degradable intermediates. Minimum mineralization ensures the process feasibility and economics. This chapter discusses WAO and ozonation as pretreatment options for complex efuent to enhance biodegradability to facilitate subsequent biodegradation via anaerobic and aerobic biological processes. Discussions pertaining to the recent developments in this area along with future challenges and prospects exemplied through relevant case studies are presented.

This study looks at the possibility of wet air oxidation (WAO) based pretreatment of complex effluent to selectively enhance the biodegradability (without substantial COD destruction) and facilitate biogas generation potential. A lab-scale wet air oxidation reactor with biomethanated distillery wastewater (B-DWW) as a model complex effluent (COD 40,000 mg L −1 ) was used to demonstrate the proof-of-concept. The studies were conducted using a designed set of experiments and reaction temperature (150–200 °C), air pressure (6–12 bar) and reaction time (15–120 min) were the main process variables of concern for WAO process optimization. WAO pretreatment of B-DWW enhanced the biodegradability of the complex wastewater by the virtue of enhancing its biodegradability index (BI) from 0.2 to 0.88, which indicate favorable Biochemical Methane Potential (BMP) for biogas generation. The kinetics of COD destruction and BI enhancement has also been reported.

The authors reviews the advancements in carbonic anhydrase– driven processes for CO2 sequestration research and engineering. Historical and recent discoveries of carbonic anhydrase and idea behind using it for CO2 sequestration are elaborated as well as the uses of this enzyme in free and immobilized forms are thoroughly discussed. New concepts such as extension of immobilized enzyme systems for bioreactor approach with the aim of CO2 abatement at the source are also introduced briefly toward the end of the review. The authors also suggest the possible future directions to employ carbonic anhydrase for CO2 sequestration.