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The objective of this study was to optimize continuous acetone-butanol-ethanol (ABE) fermentation using a two stage chemostat system integrated with liquid-liquid extraction of solvents produced in the first stage. This minimized end product inhibition by butanol and subsequently enhanced glucose utilization and solvent production in continuous cultures of Clostridium acetobutylicum B 5313. During continuous two-stage ABE fermentation, sugarcane bagasse was used as the cell holding material for the both stages and liquid-liquid extraction was performed using an oleyl alcohol and decanol mixture. An overall solvent production of 25.32g/L (acetone 5.93g/L, butanol 16.90g/L and ethanol 2.48g/L) was observed as compared to 15.98g/L in the single stage chemostat with highest solvent productivity and solvent yield of 2.5g/Lh and of 0.35g/g, respectively. Maximum glucose utilization (83.21%) at a dilution rate of 0.051/h was observed as compared to 54.38% in the single stage chemostat., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Astaxanthin (AX) is a secondary metabolite that accumulates inside the cell duringParacoccusfermentation. The fermentation biomass was extracted using supercritical carbon dioxide (SC-CO2). The solubility parameter of AX, CO2and entrainer solvents was calculated and validated with experimental results. The pressure and particle size of the biomass had a significant effect on the extraction of AX. A maximum recovery of 963.33 μg/g of AX was obtained after SC-CO2extraction at 40ºC, 350 bar and a run time of 60 min with ethanol (20% v/w) as an entrainer. Further, the experimental data has been modelled using non-linear regression analysis method. [ABSTRACT FROM PUBLISHER]

Acetone being a non-fuel solvent produced during the traditional acetone-butanol-ethanol (ABE) fermentation by Clostridium acetobutylicum ; reduces the overall fuel alcohol yield. However, the conversion of acetone into isopropanol has been recommended to improve the process economy. The present study aims to develop an engineered C. acetobutylicum DSM 792 strain to convert acetone into isopropanol by introducing the secondary alcohol dehydrogenase gene from Clostridium beijerinckii NRRL B593 using the allele-coupled exchange approach. Batch and continuous fermentation experiments were carried out with a modified strain C. acetobutylicum DSM 792-ADH to improve the isopropanol yield and titer. The growth and production behavior of the modified strain in stationary flask culture and controlled batch culture was studied. Almost 50% of acetone was converted into isopropanol with highest total solvent yield to be 0.39 g g −1 glucose. The modified strain also utilized sugar mixture and SO 2 –ethanol–water spent liquor as a substrate to produce the solvents. [ABSTRACT FROM AUTHOR]

The co-production of acetone during traditional butanol fermentation (acetone–butanol–ethanol) lowers the yield of alcohol biofuels. The present study was aimed to develop an improved Clostridium acetobutylicum strain with enhanced alcohol fuel production capability. The previously developed IBE (isopropanol-butanol-ethanol) producing C. acetobutylicum DSM792-ADH strain was further optimized to enhance the solvent productivity and yield. Immobilized cell column reactor was used to investigate the effect of dilution rate on IBE fermentation. Pure glucose, artificial sugar mixture and SEW spent liquor from spruce chips were used as substrates to study the behavior of the modified microorganism. The highest total solvent concentrations of approximately 10.60 g l −1 , 10 g l −1 and 6 g l −1 were obtained when glucose, sugar mixture and SEW spent liquor were used as substrates respectively. The modified microorganism could effectively utilize the lignocellulosic biomass hydrolyzate (SEW spent liquor) to yield a solvent productivity of 1.67 g l −1 h −1 . [ABSTRACT FROM AUTHOR]

Highlights: [•] Advanced and economical production of biobutanol. [•] Continuous two stage fermentation with integrated liquid–liquid recovery technique. [•] Utilization of lignocellulosic sugar mixture (pentoses and hexoses). [•] Long run system operation with high solvent productivity (10.85g/Lh) and yield. [•] Can be integrated to the wood based biorefinery to make it industrially feasible. [ABSTRACT FROM AUTHOR]

An unstructured model has been used to predict microbial growth based on glycerol consumption and poly-ϵ-lysine (ϵ-PL) biosynthesis by Streptomyces noursei NRRL 5126. The logistic and Luedeking-Piret equations have been proposed to describe the time course of ϵ-PL formation, substrate consumption and cell growth. The shake flask level data from kinetic studies was illustrated and compared with fermenter studies. In all cases, the model simulation matched well with the experimental observations, which made it possible to elucidate the fermentation characteristics of Streptomyces noursei during efficient ϵ-PL production from glycerol. Optimized oxygen supply into the fermenter studies shifted mixed growth associated biosynthesis of ϵ-PL from shake flask level to growth associated biosynthesis. [ABSTRACT FROM AUTHOR]

Bacteriocins are bactericidal or bacteriostatic in action and active against closely related species. Nisin is the bacteriocin produced by the lactic acid bacteria (LAB). Nisin is a small (3353 Da), cationic, hydrophobic, and 34-amino acid peptide. It is used in products such as pasteurized processed cheese, salad dressing, and liquid whole eggs to inhibit the growth of Gram-positive microorganisms including Listeria monocytogenes. The objective of the present work was to study production, purification and characterization of nisin. The production of nisin was carried out using Lactococcus lactis subsp lactis MTCC 440 by one-factor-at-a-time method and statistical design (Orthogonal array). Purification was carried out using ammonium sulphate precipitation followed by hydrophobic interaction and gel chromatography. Characterization was done for pH and temperature stability. The activity of nisin after one factor at a time optimization was found to be 5120 AU/ml. The activity of the nisin increased to 6800 AU/ml after optimization by Orthogonal Array design. Ammonium sulphate precipitation gives good yield of nisin with 60 to 80% saturation with 2.52 fold purity. The overall purification by hydrophobic interaction and gel filtration chromatography was 10.87 fold with 50.84% yield and 8.8 fold with 49.65% yield as compared to crude broth respectively. [ABSTRACT FROM AUTHOR]

The biomass obtained after the extraction of forskolin from the roots of Coleus forskohlii was evaluated as a substrate for the production of acetone-butanol-ethanol (ABE). The spent biomass constituting more than 90% of the raw material showed 50–70% carbohydrates with starch and cellulose being the major constituents. This study was undertaken to optimize enzymatic hydrolysis of C. forskohlii roots for maximum release of fermentable sugars and subsequent fermentation to ABE. The root biomass was hydrolyzed using the Stargen ® 002 and Accellerase ® 1500. Cocktail of both enzymes (16U Stargen ® 002 and 60 FPU Accellerase ® 1500) could produce 41.2 g/l of total reducing sugars (glucose equivalent to 32.33 g/l). The production of ABE was optimized in a batch fermentation using Clostridium acetobutylicum NCIM 2877. The maximum ABE production using the root hydrolysates was 0.55 g/l. Pretreatment with lime and Amberlite XAD-4 increased the production of total solvent to 5.33 g/l. [ABSTRACT FROM AUTHOR]

Increasing worldwide energy consumption and limited availability of fossil fuels propelled the researchers to develop advanced fuels (biobutanol) for its commercial development. In the present work, pea pod waste from vegetable sector was investigated for biobutanol production using C. acetobutylicum B 527 through series of steps viz. compositional analysis, drying study, saccharification, detoxification, and fermentation. Proximate analysis suggested that pea pod waste is rich in holocellulose content with 32.08% of cellulose and 21.12% of hemicellulose on dry basis and hence has a huge potential to be used as carbon source during biobutanol production. In order to enhance storability and subsequent saccharification, drying kinetics of pea pod waste was carried out in varied temperature range (60–120 °C) and the experimental data was simulated by using moisture diffusion control model. Saccharification of pea pod waste samples resulted into total sugar release of 30–48 g/L. Subsequently, 95% phenolics and 30% acetic acid were removed using activated charcoal detoxification. The acetone-butanol-ethanol (ABE) fermentation of detoxified pea pod waste slurries resulted in 4.25–5.94 g/L total solvents with about 50% sugar utilization. Overall, the utilization of pea pod waste will serve as basis for valorization of vegetable waste biomass for ABE production. [ABSTRACT FROM AUTHOR]

Present investigation explores the use of pineapple peel, a food industry waste, for acetone-butanol-ethanol (ABE) production using Clostridium acetobutylicum B 527. Proximate analysis of pineapple peel shows that it contains 35% cellulose, 19% hemicellulose, and 16% lignin on dry basis. Drying experiments on pineapple peel waste were carried out in the temperature range of 60–120 °C and experimental drying data was modeled using moisture diffusion control model to study its effect on ABE production. The production of ABE was further accomplished via acid hydrolysis, detoxification, and fermentation process. Maximum total sugar release obtained by using acid hydrolysis was 97 g/L with 95–97% and 10–50% removal of phenolics and acetic acid, respectively during detoxification process. The maximum ABE titer obtained was 5.23 g/L with 55.6% substrate consumption when samples dried at 120 °C were used as a substrate (after detoxification). [ABSTRACT FROM AUTHOR]

Fermentation products can chaotropically disorder macromolecular systems and induce oxidative stress, thus inhibiting biofuel production. Recently, the chaotropic activities of ethanol, butanol and vanillin have been quantified (5.93, 37.4, 174 kJ kg −1 m −1 respectively). Use of low temperatures and/or stabilizing (kosmotropic) substances, and other approaches, can reduce, neutralize or circumvent product-chaotropicity. However, there may be limits to the alcohol concentrations that cells can tolerate; e.g. for ethanol tolerance in the most robust Saccharomyces cerevisiae strains, these are close to both the solubility limit (<25%, w/v ethanol) and the water-activity limit of the most xerotolerant strains (0.880). Nevertheless, knowledge-based strategies to mitigate or neutralize chaotropicity could lead to major improvements in rates of product formation and yields, and also therefore in the economics of biofuel production. [ABSTRACT FROM AUTHOR]

• Butanol extraction was done using decanol and oleyl alcohol mixture. • Extraction performance was improved by using inorganic salt addition. • Sodium hydroxide addition to extractant improved butanol extraction. • Butanol extraction in packed column was optimized in presence and absence of salt. • K L a, HTU, and NTU was estimated for continuous countercurrent extraction of butanol. Product recovery is one of the essential finishing steps to any commercial fermentation process. In acetone-butanol-ethanol (ABE) fermentation, butanol recovery is quite tedious mainly due to dilute product and multiple byproduct formation in complex media. Among different recovery methods, extraction has attracted considerable attention in biofuel recovery owing to its high selectivity, low energy consumption, and ease of operation. In present work, the butanol extraction performance from synthetic solvent mixture containing ABE was tested in batch and continuous operations using 20% (v/v) decanol in oleyl alcohol. The optimized extraction conditions were then validated using actual fermentation broth to confirm effectiveness of the extraction operation. The distribution coefficient (K d) and batch extraction efficiency (E) were in the range of 5.60–9.80 and 87.70–86.90% for fermentation broth and synthetic solution, respectively for a given initial concentration of butanol in the aqueous phase. Further, E was relatively improved by supplementing different inorganic salts. Sodium hydroxide (5%, w/v) was highly effective to recover butanol from fermentation broth (E ~ 97.70%) with K d of 33.10. Besides, the continuous counter current extraction of butanol in a packed column was performed. The volumetric mass transfer coefficient (kLa) was estimated to be 0.025 1/min at an optimized superficial velocity of the aqueous phase (0.28 cm/min) and sodium hydroxide concentration (5%, w/v). Height of the extraction column was estimated to be 28.32 cm using height of transfer unit (HTU) and number of transfer unit (NTU) concept for extraction efficiency of 97.20%. Overall, the present study has demonstrated an enhanced extraction efficiency of butanol from fermentation broth. [ABSTRACT FROM AUTHOR]

• Exogenous addition of tryptophan:phenylalanine triggered butanol production. • Amino acid addition after 8 h in batch cultivation resulted in 12.43 ± 0.1 g/L butanol. • Fed-batch with in-situ product recovery was promising for improved butanol titer. • ABE production follow first order kinetics with respect to intermediate concentration. • Thermodynamics of ABE fermentation was studied to evaluate reaction feasibility. Amino acids are vital precursors in many biochemical production pathways in addition to efficient nitrogen source which could enhance microbial growth yields. Therefore, in present study, the effect of amino acids from aliphatic and aromatic family was comprehensively evaluated in batch and integrated fed batch fermentation system. Clostridium acetobutylicum NRRL B-527 was able to utilize 54.15 ± 1.0 g/L glucose to produce 12.43 ± 0.10 g/L butanol under batch cultivation. Interestingly, a significant step up in butanol titer (20.82 ± 0.33 g/L) was achieved by using fed-batch fermentation process integrated with liquid–liquid extraction module. Besides, mathematical modeling studies demonstrated the best fitting of experimental data with first order reaction kinetics. Overall, an enhancement in solvent titer by induction of essential cellular components coupled with advance bioprocess strategy was successfully utilized in this study for its further applications. [ABSTRACT FROM AUTHOR]