Hydrolysis, biomass

The compactness and complexity of (ligno)cellulose makes it much more difficult to attack by enzymes with respect to starch. Therefore, the cost of bioethanol production is higher [23], To be cost competitive with grain-derived ethanol, the enzymes used for biomass hydrolysis must become more efficient and far less expensive. In addition, the presence of non-glucose sugars in the feedstock complicates the fermentation process, because conversion of pentose sugars into ethanol is less efficient than conversion of the hexose sugars. 

A new generation of cheap enzymes for hydrolysis of cellulose and lignocellu-lose to fermentable sugars (able to complete the biomass hydrolysis during fermentation). 

Further research is also needed in this area. Particularly, (a) to create a new generation of cheap enzymes for hydrolysis of cellulose and lignocellulose to fermentable sugars (able to complete the biomass hydrolysis during fermentation) (b) to develop improved biocatalysts that allow us to simplify the process and reduce energy input and (c) to improve separation and recovery. 

Cellulase Retention and Sugar Removal by Membrane Ultrafiltration During Lignocellulosic Biomass Hydrolysis... 

In the hardwood hydrolysis experiment with the screw reactor, NREL researchers found that overmixing and an uneven flow pattern existed in the reactor. These factors have a negative effect on biomass hydrolysis. To enhance the screw conveyor reactor s performance, it was necessary to redesign the reactor to achieve adequate mixing and an even flow pattern. In the present work, CFD was utilized to analyze the flow behavior in the screw conveyor reactor, and a new screw design was proposed based on CFD analysis. 

The feedstock was mixed with 3% (w/w) sulfuric acid solution in 500-mL closed universal flasks with a liquid-to-solid ratio of 8 (w/w). The moisture content of the samples was included as water in the material balances. The mixtures were allowed to stand for 10 min at room temperature in order to equilibrate the acid concentrations between the bulk phase and biomass. Hydrolysis was performed in an autoclave at 130°C for pre-established isothermal periods ranging from 2 to 240 min. The flasks were placed inside the autoclave at 100°C, and the heating time to reach 130°C was recorded. After the reaction time had elapsed, the autoclave was rapidly cooled down and the hydrolysate and solid phase were recovered by filtration (Whatman no. 1 filter paper). All experiments were done at least in duplicate. 

Vick Roy, J.R. Converse, A.O. Biomass hydrolysis with sulfur dioxide and water in the region of the critical point. In Supercritical Fluid Technology, Penniger, J.M.L., Radosz, M., McHugh, M.A., Krukonis, V.J., Eds. Elsevier Amsterdam, 1985 397-414. 

Taken together, the results of this research demonstrate the importance of knowing and regulating the starch and soluble protein contents of wheat bran supplements from different sources when adding wheat bran to stimulate cellulase and xylanase production by P. decumbens. Our results also predict that adding cello-oligosaccharides directly to P. decumhens fermentation could significantly improve industrial-scale biomass hydrolysis by P. decumbens. 

The major products, catechol, 2,3-dihydroxyacetophenone, and 3,8-dihydroxy-2-methylchromone, as well as 2-furaldehyde, were quantitatively determined in the acidic reaction mixtures of xylose and glucuronic acid. Considerable variation of these components occurred within pH 1.7-4.0. Such products, potentially produced during biomass hydrolysis, may have an inhibiting effect on subsequent fermentation processes. 

Hu, C., Zhao, X., Zhao, J., Wu, S. et al (2009) Effects of biomass hydrolysis by-products on oleaginous yeast Rkodosporidium toruloides. Bioresour. Technol, 100, 4843-4847. 

Harris PV, Weiner D, McFarland KC, Re E, Navarro Poulsen JC, Brown K, Salbo R, Ding H, Vlasenko E, Merino S, Xu F, Cherry J, Larsen S, Lo Leggio L. (2010). Stimulation of lignocellulosic biomass hydrolysis by proteins of glycoside hydrolase family 61 structure and function of a large, enigmatic farmly. Biochemistry, 49(15), 3305-3316. 

Knutsen JS, Davis RH. (2004). Cellulase retention and sugar removal hy membrane ultra-filtration during lignocellulosic biomass hydrolysis. Appl Biochem Biotechnol, 114, 585-599. 

From an industrial perspective, the use of carbohydrate-active enzymes as cost effective, selective catalysts of biomass hydrolysis has been growing steadily over the last century (5). In particular, carbohydrases play key roles in the starch processing, animal feed, textile, and pulp and paper industries (5-7) (Table 1). The observation that enzymatic starch processing alone accounted for nearly 10% of the U.S. 1.4 billion enzyme market (1998 values) further underscores the importance of these catalysts (6). The use of (hemi)cellulose-degrading enzymes to saccharify biomass as a precursor to biofuels production and other bioreflnery purposes are of particular contemporary interest in the quest to reduce fossil fuel dependence (5,8,9). 

Katzen R, Schell DJ. Lignocellulosic feedstock biorefmery history and plant development for biomass hydrolysis. In Kamm B, Gruber PR, Kamm M, editors. Biorefineries - industrial processes and products, vol. 1. Weinheim (Germany) Wiley-VCH 2006. p. 129—38. 

Borozdinskaya et al. [98] reported on a process in which amino acids from activated sludge biomass hydrolysis were acylated with caproyl chloride at 80°C for 1 h (pH 7.5-8.5) to produce surfactants having a surface tension of 33.1-65.1 mN/m, viscosity of 1.08-1.25 cSt, a moisture content of 75.6-98.5%, and a cmc of 0.04-0.21 g/L. Surfactants based on glycine had the highest surface activity and high foaming power [98]. 

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