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High-protein algae bioproduct system boundaries for environmental sustainability risk analysis.

In the last 20 years, biodiesel consumption in the United States has rapidly increased to ∼2 billion gallons per year as a renewable supplement to fossil fuel. However, further expansion of biodies...

Sustainable biorefinery heavily depends on the generation of value-added products, particularly from lignin. Despite considerable efforts, the production of fungible lignin bioproducts is still hindered by the poor fractionation and low reactivity of lignin. To address these challenges, the sequential organosolv fragmentation approach (SOFA) using ethanol plus different-stage catalysts was explored to selectively dissolve lignin for producing multiple uniform lignin streams, and to tailor its chemistry and reactivity for fabricating lignin nanoparticles (LNPs) with desired quality features. In a biorefinery concept, the carbohydrate output is taken into consideration. SOFA significantly increased the glucose and xylose yields, suggesting an improved monomer-sugar release. The fractionated lignin was used to fabricate LNPs via self-assembly. Although these LNPs were derived from the same substrate, they exhibited different properties. The effective diameter almost followed the order of stage 1, stage 3, and stage 2 in each SOFA, and the smallest effective diameter was approximately 130 nm from SOFA using ethanol plus sulfuric acid. The polydispersity index and zeta potential were less than 0.08 and −50 mV, respectively, suggesting good uniformity and stability of the LNPs. Lignin characterization results suggested that SOFA using ethanol plus sulfuric acid produced high-molecular-weight lignin, decreased S/G ratio, and β-O-4 and β–β linkage abundance, yet produced the condensed lignin and enhanced its hydrophobicity. More importantly, it exposed more phenolic OH groups and enhanced the stability of LNPs, likely due to the hydrogen bond networks. Together with enriched COOH groups, it promoted the formation of electrical double layers and increased the zeta potential of LNPs. As a result, by tailoring the lignin chemistry using SOFA to enhance the self-assembling process, high-quality LNPs of a spherical shape, small effective diameters, and good stability have been fabricated, which represents a sustainable means for upgrading the low-value lignin and thus contributes to the profitability of biorefineries.

Lignin valorization is essential for a sustainable and economically viable biorefinery. Despite the recent efforts, it is still unclear how the reactivity of native lignin can be improved by pretreatment in a biorefinery and how different components in biorefinery residue especially residual sugar contribute to bioconversion in biorefineries. In the present study, co-utilization of lignin and limited glucose was first evaluated and proved to facilitate lignin conversion and polyhydroxyalkanoate (PHA) production. A new integrated biorefinery was then designed to cooperatively valorize lignin and residual sugar for improving the PHA yield and utilization efficiency of biorefinery residue. By the design of integrated biorefinery, the glucose and xylose yield were 91% and 73%, respectively, which increased by 18% and 12% compared with that only using sodium hydroxide pretreatment. Approximately 85% of the lignin was dissolved into a liquid stream with the integrated biorefinery, corresponding to an increase of 69% compared with that only using sodium hydroxide pretreatment. More than 70% of the residual sugar was released from the biorefinery residue, producing the soluble lignin stream that contains both lignin and residual sugar for synergistic bioconversion. Bioconversion of the soluble lignin stream with Pseudomonas putida KT2440 produced 1.5 g l−1 PHA, representing the record titer of PHA from biorefinery residue. The lignin characterization results from nuclear magnetic resonance and gel-permeation chromatography showed that the integrated process significantly reduced the lignin molecular weight, broke down more β-O-4 and β-5 linkages, and enriched the H-lignin content. Alongside the increased residual sugar concentration, the bioconversion performance of soluble lignin to PHA was significantly improved. Overall, the integrated biorefinery increased the fermentable sugar yield and improved the PHA production from biorefinery waste by cooperative valorization of lignin and residual sugar, which shows potential advantages for biorefinery sustainability.

To make biorefineries sustainable, codesign of fractionation technologies and lignin valorization has been found to be essential. Combinatorial organosolv pretreatment (COP) was thus developed in a...

The formation of lignin-like structures by the degradation primarily of plant polysaccharides has been observed after the severe thermochemical acidic pretreatment of lignocellulosic biomass. These structures were found to be deposited as droplets and microspheres on the surface of solid biomass residue and/or in liquid effluent. These structures showed lignin-like properties and yielded a positive Klason lignin (K-lignin) value, and are termed pseudo-lignins and/or humins. Pseudo-lignin is an aromatic material containing hydroxyl and carbonyl functional groups, which contributes to K-lignin values but is not derived thereof. Pseudo-lignin arises from the polymerization/condensation reactions from key intermediates such as 3,8-dihydroxy-2-methylchromone and 1,2,4-benzenetriol derived from furfural (FF) and 5-hydroxymethylfurfural (5-HMF), respectively. Furthermore, pseudo-lignin retards the biological conversion of pretreated biomass through unproductive binding to enzymes/microbes and a physical hindrance to enzymes and microbes by blocking the active cellulose surface binding sites. This necessitates a fundamental understanding of the pseudo-lignin structure and its effect on biomass recalcitrance. This review examines the pseudo-lignin formation during acidic and hydrothermal biomass pretreatments and the cooling process after pretreatment, which are applied to biomass for biofuel synthesis through a biochemical route. The review article is divided into five parts: the first part gives the background information on pseudo-lignin formation during different pretreatment processes for the conversion of biomass to biofuels, the second part focuses on the chemistry and mechanism of pseudo-lignin formation, the third part emphases on the different analytical techniques used for pseudo-lignin characterization and recalcitrance elucidation, the fourth part illustrates the recalcitrance behaviour of pseudo-lignin, and the fifth part deals with the practical consideration regarding the design of the processes for the prevention of pseudo-lignin formation.

Lignocellulosic biorefineries have gained much attention worldwide as a potential solution to the challenges of energy demand and global climate change. However, the industrial implementation of biorefineries has been hindered by low fermentable sugar yields and low lignin processability. Combinatorial pretreatments with a low holding temperature were investigated in an effort to synergistically improve the carbohydrate output and lignin processability from corn stover. Upon combinatorial pretreatment with 1% H2SO4 for 30 min followed by 1% NaOH for 60 min at 120 °C, glucan and xylan conversion increased by 11.2% and 8.3% respectively relative to single pretreatment. This combinational pretreatment removed the amorphous portion, disrupted the rigid structure, and increased the water holding capacity of corn stover, thus increasing the hydrolysis performance. With whole fractionation by combinatorial pretreatment, glucose and xylose yields were 88.4% and 72.6%, respectively, representing increases of 10.0% and 8.1%. The lignin yield was 19.7% in the solid residue and 77.6% in the liquid stream, which increased by 33.4%. When grown in fed-batch fermentation mode, a record level of polyhydroxyalkanoate (PHA) concentration (1.0 g l−1) was obtained using lignin as a carbon source by Pseudomonas putida KT2440. Lignin characterization results showed that combinatorial pretreatment increased the G- and H-lignin content, reduced the β–β and β-O-4 groups, and fractionated more aromatic monomers, thus facilitating lignin processability into PHA. These results highlighted the use of combinational pretreatment at a low holding temperature as a means to synergistically maximize the carbohydrate output and lignin processability, which provides a unique set of features to improve the biorefining performance.

We demonstrated production of a superior performance biodiesel referred to here as fatty acid fusel alcohol esters (FAFE) – by reacting fusel alcohols (isobutanol, 3-methyl-1-butanol, and (S)-(-)-2-methyl-1-butanol) with oil (glyceryl trioleate) using lipase from Aspergillus oryzae. Reaction conditions corresponding to a molar ratio of 5:1 (fusel alcohols to oil), enzyme loading of 2% w/w, reaction temperature of 35 °C, shaking speed of 250 rpm, and reaction time of 24 h achieved >97% conversion to FAFE. Further, FAFE obtained from reacting a fusel alcohol mixture with corn oil were evaluated for use as a fuel for diesel engines. FAFE mixtures showed superior combustion and cold-flow properties, with the derived cetane numbers up to 4.8 points higher, cloud points up to −6 °C lower, and the heat of combustion up to 2.1% higher than the corresponding FAME samples, depending on the fusel mixture used. This represents a significant improvement for all three metrics, which are typically anti-correlated. FAFE provides a new opportunity for expanded usage of biodiesel by addressing feedstock limitations, fuel performance, and low temperature tolerance.

Proper timing of switchgrass harvest for bioenergy is important to maximize yield and optimize end use conversion. Proposed windows range from peak biomass to the following spring after overwintering in the field. There are various pros and cons associated with harvest timing: earlier harvests maximize yield but can remove nutrients from the field that may require replacement, while later harvests have reduced biomass yields due to weathering but maximize nutrient resorption in belowground tissues. Switchgrass composition changes during the harvest period, with losses of potential fermentation nutrients (amino acids and minerals), and sources of pretreatment-derived inhibitors (soluble sugars), which could affect downstream conversion by microorganisms. For this work we investigated whether switchgrass harvest could be timed to maximize beneficial impacts on fermentation. Switchgrass samples were harvested from five replicate field plots in Wisconsin, roughly every 2-3 weeks from peak biomass (Aug. 20) until after the killing frost (Nov. 7). Cell wall composition showed little consistent variation with harvest date while bulk biomass analysis showed a relative increase in cell wall content (lignin and structural sugars) and loss of extractives (minerals, protein, soluble sugars, and others). Following high or low severity AFEX pretreatment and high solids enzymatic hydrolysis (6% glucan loading), two field replicates were fermented using Saccharomyces cerevisiae 424A, a strain engineered to utilize xylose in addition to glucose. For both pretreatment severities, S. cerevisiae 424A grown in hydrolysates from the three earlier harvests utilized only a small fraction of available xylose, while almost complete utilization occurred within 96 hr for the last three harvest dates. Detailed analysis of the hydrolysate low molecular weight aromatics did not indicate any compounds potentially responsible for the inhibition, with most of the observed variation in their concentration due to pretreatment severity. Amino acid composition also did not appear to be limiting. Current indications point to a plant-generated compound that degrades during senescence, which future work will attempt to identify. Ultimately this work demonstrates that, although an attractive option to maximize yield, harvesting switchgrass before it begins senescing could have a negative effect on downstream conversion processes.

Deconstruction with low-cost ionic liquids (ionoSolv) is a promising method to pre-condition lignocellulosic biomass for the production of renewable fuels, materials and chemicals. This study investigated process intensification strategies for ionoSolv pretreatment of Miscanthus × giganteus with the low-cost ionic liquid triethylammonium hydrogen sulfate ([TEA][HSO4]) in the presence of 20 wt% water, using high temperatures and a high solid to solvent loading of 1 : 5 g/g. The temperatures investigated were 150, 160, 170 and 180 °C. We discuss the effect of pretreatment temperature on lignin and hemicellulose removal, cellulose degradation and enzymatic saccharification yields. We report that very good fractionation can be achieved across all investigated temperatures, including an enzymatic saccharification yield exceeding 75% of the theoretical maximum after only 15 min of treatment at 180 °C. We further characterised the recovered lignins, which established some tunability of the hydroxyl group content, subunit composition, connectivity and molecular weight distribution in the isolated lignin while maintaining maximum saccharification yield. This drastic reduction of pretreatment time at increased biomass loading without a yield penalty is promising for the development of a commercial ionoSolv pretreatment process.

Microwave assisted biocatalytic transformation is a green process for chiral drug resolution. Different immobilized enzymes such as Novozym 435, Lipozyme TL IM, Lipozyme RM IM, Lipase Amano AS and Lipase AYS amino were screened for the kinetic resolution of RS-(±)-ketorolac under microwave irradiation. To study kinetics and mechanism, the effect of different parameters on the conversion, initial rates and enantiomeric excess of substrate were studied. Under microwave synergism, an increase in initial rates up to 1.5-fold was observed. Novozym 435 effectively catalyzed the enantioselective esterification of RS-(±)-ketorolac, showing excellent conversion (50%) and enantiomeric excess (>99%) in 3 h at 50 °C and 300 rpm. Based on initial rate and progress curve data, the reaction was found to follow the Ping Pong bi–bi mechanism with inhibition by n-octanol.

Cinnamate esters have gained importance due to their unique antioxidant, flavor, and fragrance properties. Synergism of microwave irradiation and enzyme catalysis was investigated in transesterification of ethyl cinnamate and geraniol. Effects of different operat- ing parameters such as biocatalyst, solvent, and temperature were first studied. An increase in initial rates up to 4.2-fold was observed under microwave irradiation vis-a-vis conventional heating. Further, the Taguchi L16 (4*4) orthogonal array design with four level-four variables and 16 run was employed for the optimization of parameters including enzyme loading, temperature, speed of agitation, and substrate mole ratio. Optimal conditions obtained via the Taguchi approach were as follows: enzyme loading, 60 mg; temperature, 65 °C; speed of agitation, 300 rpm; and substrate mole ratio, 1:2. The analysis of initial rate data established the validity of the ternary complex ordered bi-bi mechanism with inhibition by geraniol. The experimental data fitted very well with the model predictions.

4-Chloro-2-methylphenoxyacetic acid (MCPA) is a selective systemic herbicide which is absorbed by leaves and roots. MCPA esters are preferred due to their low water solubility and environmental friendliness. Esterification of MCPA with n-butanol was investigated as a model reaction using immobilized enzymes under the influence of microwave irradiation. Different immobilized enzymes such as Novozym 435, Lipozyme TL IM, Lipozyme RM IM and Lipase AYS Amano were studied under microwave irradiation amongst which Novozym 435 (immobilized Candida antarctica lipase B) was the best catalyst. Effects of various parameters were systematically studied on rates and conversion. Under microwave irradiation, the initial rates were observed to increase up to 2-fold. Under optimized conditions of 0.1 mmol MCPA and 0.3 mmol n-butanol in 15 mL 1,4-dioxane as solvent, Novozym 435 showed a conversion of 83% at 60 °C in 6 h. Based on initial rate and progress curve data, the reaction was shown to follow the Ping Pong bi–bi mechanism with inhibition by MCPA and n-butanol. Esterification of MCPA was also studied with different alcohols such as isopropyl alcohol, n-pentanol, n-hexanol, benzyl alcohol and 2-ethyl-1-hexanol.

Alkyl benzoate esters have gained importance due to their application in a variety of industries such as flavor, cosmetics, and pharmaceuticals. Effect of microwave irradiation in the enzymatic transesterification of methyl benzoate with different alcohols, viz., n-butanol, n-pentanol, n-hexanol, n-octanol, benzyl alcohol, isoamyl alcohol, and 2-ethyl-1-hexanol, was investigated. Synthesis of n-hexyl benzoate was chosen as the model reaction. Different enzymes such as Novozym 435, Lipozyme TL IM, Lipozyme RM IM, and Lipase AYS Amano were screened under microwave irradiation. Novozym 435 was the most active catalyst. To establish the kinetics and mechanism for Novozym 435 catalyzed transesterification of methyl benzoate with n-hexanol, the effects of various parameters affecting the conversion and rate of reaction were studied. Under microwave synergism, an increase in initial rates up to 6.5-fold was observed. Twenty millimoles of methyl benzoate and 10 mmol of n-hexanol in n-heptane with immobilized Cand...

The piston is considered as most important part of I.C engine. High temperature produced in an I.C engine may contribute to high thermal stresses. Without appropriate heat transfer mechanism, the piston crown would operate ineffectively which reduce life cycle of piston and hence mechanical efficiency of engine. The literature survey shows that ideal piston consumes heat produced by burnt gases resulting in decrease of Engine overall Efficiency. In this project work an attempt is made to redesign piston crown using TBC on piston surface and to study its Performance. A 150 cc engine is considered and TBC material with different thickness is coated on the piston. 3D modeling of the piston geometry is done 3D designing software Solidworks2015. Finite Element analysis is used to calculate temperature and heat flux distribution on piston crown. The result shows TBC as a coating on piston crown surface reduces the heat transfer rate within the piston and that will results in increase of engine efficiency. Results also show that temperature and heat flux decreases with increase in coating thickness of YSZ.