https://faculty.washington.edu/renatab/courses/PSE490/downloads/pretreatment.pdf

Features of promising technologies for pretreatment of lignocellulosic biomass.

Hydrolysis of lignocellulosic materials for ethanol production: a review.

Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for "consolidated bioprocessing" (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.

/pdf/microbial-cellulose-utilization-fundamentals-and-4yec12qx1c.pdf

Microbial cellulose utilization: fundamentals and biotechnology.

Pretreatments to enhance the digestibility of lignocellulosic biomass

Biofuels produced from various lignocellulosic materials, such as wood, agricultural, or forest residues, have the potential to be a valuable substitute for, or complement to, gasoline. Many physicochemical structural and compositional factors hinder the hydrolysis of cellulose present in biomass to sugars and other organic compounds that can later be converted to fuels. The goal of pretreatment is to make the cellulose accessible to hydrolysis for conversion to fuels. Various pretreatment techniques change the physical and chemical structure of the lignocellulosic biomass and improve hydrolysis rates. During the past few years a large number of pretreatment methods have been developed, including alkali treatment, ammonia explosion, and others. Many methods have been shown to result in high sugar yields, above 90% of the theoretical yield for lignocellulosic biomasses such as woods, grasses, corn, and so on. In this review, we discuss the various pretreatment process methods and the recent literature that...

http://ucce.ucdavis.edu/files/datastore/234-1388.pdf

Methods for Pretreatment of Lignocellulosic Biomass for Efficient Hydrolysis and Biofuel Production

Hard and softwoods were pretreated by mild acid hydrolysis and their pore size distribution determined. Regardless of the substrate, the initial rate of hydrolysis using cellulase from Trichoderma reesei is linearly correlated with the pore volume of the substrate accessible to a nominal diameter of 51 A representative of the size of the cellulase. In contrast, crystallinity index has no relationship to the rate of hydrolysis.

The Effect of Pore Size Distribution on the Rate of Enzymatic Hydrolysis of Cellulosic Substrates

Effect of steam explosion pretreatment on pore size and enzymatic hydrolysis of poplar

A method of distillation employing a heat pump (which may be driven by a compressor) using a vapor stream from within the distillation system as a heat source and a liquid stream from within the distillation system as a heat sink. The selection of heat-source vapors and heat-sink liquid is such that at least one is withdrawn from the phase-contracting region of the distillation system. The return of streams withdrawn from the phase-contacting region of the distillation system to the distillation system is such that at least one of the streams is returned at a temperature different from that of the point from which it was withdrawn, and all withdrawn streams are returned in manner such that a stream removed as vapor is returned at a point with a temperature at most that at the point it was withdrawn, and a stream removed as liquid is returned at a point with a temperature at least that at which it was withdrawn. Embodiments of the basic method where vapor only, liquid only, or both liquid and vapor are withdrawn from and returned to the phase-contacting region of the distillation system are considered. The impact of the invention is to reduce the heat requirement of distillation in exchange for an amount of work which is usually small because the temperature difference between heat sources and sinks is minimized. Combination of the basic distillation method with multi-effect distillation, convention overhead-to-reboiler heat pumped distillation, azeotropic and extractive distillation, and fermentative production of volatile compounds is described. A system specifically designed for the separation of ethanol-water mixtures which utilizes the present invention and extractive distillation in a system with extensive heat integration is presented.

Distillation process for ethanol

Partial acid hydrolysis was studied as a per treatment to enhance enzymatic hydrolysis, such a pretreatment was carried out in a continuous flow reactor on oak corn Stover, newsprint, and Solka Floc at temperatures ranging from 160 to 220°C, acid concentration ranging from 0 to 1.2%, and a fixed treatment time of 0.22 min. The resulting slurries and solids were than hydrolyzed with Trichoderma ressei QM 9414 cellulase at 50°C for 48 hr. For all substrates except Solka Floc, increased glucose yields were achieved during enzymatic hydrolysis of the pretreated materials as compared to hydrolysis of the original substrate. In several cases, after pretreatment, 100° of the potential glucose content of the substrate was converted to glucose after 24hr of enzymatic hydrolysis. It is felt that the increased glucose yields achieved after this pretreatment are due to acid's removal of hemicellulose, reduced degree of polymerization, and possibly due to a change in the crystal structure of the cellulose.

Hans E. Grethlein

Papers

The Effect of Pore Size Distribution on the Rate of Enzymatic Hydrolysis of Cellulosic Substrates

Effect of steam explosion pretreatment on pore size and enzymatic hydrolysis of poplar

Distillation process for ethanol

Partial acid hydrolysis of cellulosic materials as a pretreatment for enzymatic hydrolysis

Common aspects of acid prehydrolysis and steam explosion for pretreating wood