Enhancement of ethanol production in the presence of metabolic inhibitors inClostridium thermocellum strain SS8

Summary Clostridium thermocellum strain SS8 produced 0.25g of ethanol and 0.24g of acetic acid per g cellulose consumed. Enhancement in ethanol production upto 0.39g/g substrate was observed in the presence of 0.15mM concentration of sodium azide and 7% polyethyleneglycol along with significant repression in acetic acid formation.     

Cellulase and hemicellulase production by Cellulomonas flavigena NIAB 441

Summary Cellulomonas flavigena (strain NIAB 441) produced cellulase and hemicellulase activities when grown on Leptochloa fusca L. Kunth (Kallar grass), found to be the best inducer for enzyme production. The enzyme possessed the potential to saccharify bagasse, Kallar grass straw, wheat straw, carboxymethyl cellulose (CMC) and xylan to reducing sugars.     

Cellulase and xylanase production by Trichoderma reesei Rut C-30

Summary When grown on cellulose or xylan, Trichoderma reesei (strain Rut C-30) produced extra-cellular enzymes which could hydrolyze both cellulose and xylan to their respective monosaccharides. At low O₂ saturation, -glucosidase activity is greatly reduced for cellulose-grown but not xylan-grown cells.     

A one step process for the conversion of cellulose to ethanol using anaerobic microorganisms in mono- and co-culture

Summary The reducing sugars, glucose, and ethanol produced during growth of the anaerobes Clostridium thermocellum and Acetivibrio cellulolyticus on cellulose were assayed. Zymomonas mobilis was grown under similar conditions and could ferment glucose to ethanol. The ethanol production by the cellulolytic bacteria alone and in co-culture with Zymomonas is described. Approximately 27% of a 1% cellulose substrate could be converted to ethanol by this co-culture.     

Effects of agitation on enzymatic saccharification of cellulose

Summary Crystalline cellulose Avicel has been hydrolyzed byTrichoderma viride cellulase (Meicelase CEPB) under vaned agitation conditions and the effect of agitation on the adsorption of cellulase on cellulose has been studied. Agitation was found to enhance the hydrolysis pf crystalline cellulose; possibly the agitation enhances the adsorption of exoglucanase to shift the adsorption balance of exoglucanase and endoglucanase to a direction favorable for their synergistic action on the surface of cellulose.     

Alternative pathway for glucose production from cellulose using Trichoderma reesei QM9414 cellulase

Summary Evidence is presented which supports the view that two routes exist for the formation of glucose when cellulosic material is saccharified using T. reesei enzyme preparations. The first is via cellobiose and for the second, glucose appears to be formed by a route not involving cellobiose. The second route becomes more apparent when dealing with less crystalline cellulose. This should be considered when constructing strains to produce enzyme preparations for saccharification of less crystalline cellulose.     

A continuous thermophilic cellulose fermentation in an upflow reactor by aClostridium thermocellum-containing mixed culture

Summary A continuous thermophilic cellulose fermentation by aCl. thermocellum-containing mixed culture was carried out in an upflow reactor for a period of 100 days. The cellulose conversion rate was finally 0.35 g.1^–1.h^–1. Evidence that the fermentation process was influenced by both pH and dilution rate was given by the changes of concentration of the main fermentation products, acetic acid and ethanol. The role of cellodextrins and glucose as reactive intermediates in the process of cellulose breakdown was established.     

Extracellular invertase from Aspergillus athecius: Isolation and immobilization

Summary A fungal strain isolated from soil and identified asAspergillus athecius, when grown on moistened wheat bran produced large amounts of extracellular invertase. Most of the invertase from the moldy bran was easily extracted by low ionic strength buffer (0.005 M, pH 5.7). The crude invertase immobilized on DEAE cellulose showed not only increased activity (45%) but also greater thermal and storage stability than the free enzyme. The free and the bound enzymes showed a temperature optimum of 50–55°C and a pH optimum of 5.7 and 4.8 respectively. The K_m app. of the bound enzyme was lower than that of the free enzyme.     

Effects of aqueous sulfur dioxide on cellulose

Summary The reaction of aqueous sulfur dioxide with cellulose pulp and cotton linters was investigated to determine the effect of this lignocellulosic pretreatment method on the cellulosic portion. Sulfur dioxide treatment dramatically reduced the DP of the cellulose but did not affect its enzymatic digestibility, and did not decrystallize the cellulose as recently reported by Leeet al. (1979).Maintained in cooperation with the University of Wisconsin, Madison, Wis.     

Partial characterization of anEscherichia coll strain harboring a xylanase encoding plasmid

Summary The plasmid pRH271, harboring a xylanase gene cioned fromBacilius subtilis, has been transferred into a mutant ofE. coli SK2284 which allowed the release of part of the xylanase in the culture supernatant. Kinetic parameters of this recombinantE. coll strain were determined in microscale batch culture with and without the selective pressure of antibiotics. No significant difference in µ_max was observed for the nontransformedE. coli strain when compared to the recombinant strain. However, K₅ values for glucose were two times higher in the case of the recombinant strain. Preliminary study of xylanase production in a large batch farmenter was also described.     

Cellulase production byTalaromyces emersonii CBS 814.70 co-immobilized with cellulose in calcium alginate

Summary The thermophilic fungusTalaromyces emersonii CBS 814.70 was co-immobilized with cellulose in calcium alginate beads. Cellulose production by this system was compared with a conventional process. The immobilized system continued to produce enzyme in a batch-fed reactor system while the non-immobilized had ceased production; levels of enzyme produced by the immobilized system were almost twice the maximum produced by the non-immobilized system.     

Effect of intermittent feeding of cellulose hydrolyzate to hemicellulose hydrolyzate on ethanol yield byPachysolen tannophilus

Summary Intermittent-feeding of cellulose hydrolyzate to hemicellulose hydrolyzate of hardwood resulted in greater yields of ethanol usingPachysolen tannophilus than batch fermentations of either hydrolyzate alone or as a mix. Conversion efficiencies as great as 0.40 g ethanol/g sugar fed were achieved.     

Solid state fermentation of oat straw by Polyporus sp A-336 and the effect of added sugars

Summary Supplementing oat straw in SSF by Polyporus sp A-336 with xylose, mannose, glucose and arabinogalactan at levels of 5 and 10% of straw weight stimulated lignin degradation and cellulose hydrolysis. Degradation of lignin, hemicellulose and cellulose was monitored for 30 days in plain straw, and straw plus xylose and showed that xylose shortened the lag in lignin breakdown and slowed hemicellulose utilization. At 24 days, similar polymer losses occurred in both systems and enzymatic cellulose hydrolysis had reached a maximum of 47% weight loss.     

Use of charcoal to minimize end product inhibition in enzymatic hydrolysis of cellulose

Summary Tests made to improve saccharification of cellulose byTrichoderma cellulases showed that charcoal used as an adsorbent minimized the end product inhibition. Charcoal adsorbed both cellobiose and glucose and did not affect the enzymatic hydrolysis of cellulose. Results showed that charcoal is as effective as -glucosidase in improving the enzymatic saccharification of cellulose.     

Solid state fermentation and fractionation of oat straw by Basidiomycetes

Summary Seventee white-rot and brown-rot fungi were screened for their ability to fractionate the lignocellulose structure of oat straw through the preferential attack of lignin or cellulose. Fermentations were carried out under solid-state conditions with 25 g quantities of straw. The fermented straw was analyzed for weight loss, Klason lignin loss and cellulase digestion. All the fungi attacked both lignin and carbohydrate fractions causing 3–28% weight losses and 26–34 g/100 g enzymatic digestibility. Polyporus tulipiferae, Phanerochaete chrysosporium and Polyporus sp. were tested for the effects of various nitrogen, phosphate and carbon levels, incubation temperatures and incubation time. The three fungi had different responses to these factors.     

Ethanol production byClostridium thermocellum SS8, a newly isolated thermophilic bacterium

Summary Clostridium thermocellum SS8, has a broad substrate spectrum. It produced 0.25–0.29 g. of ethanol per g. of cellulose consumed. Cellulose fermentation was repressed by both glucose and cellobiose. pH had an effect on ethanol productivity at high substrate concentration. Best results were obtained at 30 g/l with an E/S and E/A ratios of 0.29 and 2.4 respectively.     

Estimation of fungal growth on lignocellulosic substrates using an enzyme-linked immunosorbent assay

Summary The feasibility of using an enzyme-linked immunosorbent assay (ELISA) for quantifying the growth ofThielavia terrestris on cellulosic substrates was studied. WhenT. terrestris was grown, using glucose as the substrate, the ELISA readings correlated well with the mycelial dry weight values. When lignocellulosic substrates were used, the ELISA appeared to slightly overestimate fungal growth. The ELISA values indicated that the fungi grew more slowly on steam-treated aspenwood than on commercial sources of cellulose (Avicel).     

Ethanolic fermentation of cane molasses by a highly flocculent yeast

Summary A study of the comparative kinetics of standardS.uvarum ATCC 26602 withS.cerevisiae Y-10 (an isolate) and a highly flocculent strain ofS.uvarum in batch mode has shown that both the isolate and the highly flocculentS. uvarum strain have more desirable characteristics than the standard strains for ethanol production from cane molasses.     

Some characteristics of the cellulolytic enzyme system of Chaetomium cellulolyticum

Summary The effects of pH and temperature on the activities of endoglucanase, exoglucanase and -glucosidase of C. cellulolyticum were studied. Thermal stability of these enzymes was characterized. Enzymatic hydrolyses of cellulose were performed yielding predominantly glucose and cellobiose. Glucose was shown to be a potent inhibitor of its own formation in cellulose saccharification.     

Kinetic studies on alac-containing strain ofZymomonas mobilis

Summary Batch and continuous culture studies have been carried out on a strain ofZ.mobilis (ZM6306) which can convert lactose directly to ethanol. Previous strain development has established that thelac operon encoded on the transposon Tn951 can be expressed inZ.mobilis. Using a medium containing 80 g/l glucose and 40 g/l lactose, it was found that strain ZM6306 could convert about 13 g/l lactose to 4 g/l ethanol and 6 g/l galactose in continuous culture. Further lactose conversion is likely with increased cell concentration using a cell recycle system.