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Concentrated dilute acid hydrolysate was obtained from hot water extracts of Acer saccharum (sugar maple) and was fermented to ethanol by Pichia stipitis in a 1.3-L-benchtop bioreactor. The conditions under which the highest ethanol yield was achieved were when the air flow rate was set to 100 cm(3) and the agitation rate was set to 150 rpm resulting in an overall mass transfer coefficient (K(L)a) of 0.108 min(-1). A maximum ethanol concentration of 29.7 g/L was achieved after 120 h of fermentation; however, after 90 h of fermentation, the ethanol concentration was only slightly lower at 29.1 g/L with a yield of 0.39 g ethanol per gram of sugar consumed. Using the same air flow rate and adjusting the agitation rate resulted in lower ethanol yields of 0.25 g/g at 50 rpm and 0.30 g/g at 300 rpm. The time it takes to reach the maximum ethanol concentration was also affected by the agitation rate. The ethanol concentration continued to increase even after 130 h of fermentation when the agitation rate was set at 50 rpm, whereas the maximum ethanol concentration was reached after only 68.5 h at 300 rpm.

In this study the influence of the insoluble solids in nano-filtrated sugar maple hemicellulosic hydrolysate on the metabolic behavior of Pichia stiptis was investigated. The particle properties of hemicellulosic hydrolysate were analyzed. Phosphoric acid and ammonium (PA) were applied to remove the particles. The metabolic behavior and growth property of P. stipitis in particle--removed hydrolysate was measured. Results demonstrated that the average particle size and zeta potential of the untreated hydrolysate were 2266.9±78.2 nm and -6.09±0.49 mV. Xylose consumption and ethanol production rate were significantly decreased when particle content is greater than 1.63 g/L. Because the majority of particles (34 g/L) were removed from hydrolysates by phosphoric acid and ammonium treatment, the fermentability of the hydrolysate was significantly improved. These results indicated particles play an important role in hydrolysate inhibition effect., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Recombinant Volvariella volvacea endoglucanase 1 (EG1) and its catalytic module (EG1-CM) were obtained by expression in Pichia pastoris, purified by two-step chromatography, and the catalytic activities and binding capacities were compared. EG1 and EG1-CM exhibited very similar specific activities towards the soluble substrates carboxymethyl cellulose, lichenan and mannan, and insoluble H(3)PO(4) acid-swollen cellulose, whereas the specific activities of EG1-CM towards the insoluble substrates alpha-cellulose, Avicel and filter paper were approximately 58, 43 and 38%, respectively compared to EG1. No increase in reducing sugar release was detected in the reaction mixture supernatants after 50h exposure of filter paper, Avicel or alpha-cellulose to EG1-CM, whereas increases in the total reducing sugar equivalents (i.e. reducing sugar released into solution together with new reducing ends generated in the cellulosic substrates) in reaction mixtures were observed after 1h. In reaction mixtures containing EG1, soluble reducing sugar equivalents were detected in supernatants after 3h incubation with the insoluble cellulosic substrates. EG1-CM did not adsorb to Avicel, and the binding capacities of EG1-CM towards filter paper and H(3)PO(4) acid-swollen cellulose were 27.9-33.3% and 29.6-60.6%, respectively of values obtained with EG1 within the range of total added protein. In enzymatic deinking experiments, the ink removal rate in EG1-CM-treated samples was only slightly higher (approximately 8%), than that of untreated controls, whereas that of the EG1-treated samples was 100% higher. Bio-stoning of denim with EG1-CM resulted in increases of 48% and 40% in weight loss and indigo dye removal, respectively compared with untreated controls. These increases were considerably lower than the corresponding values of 219% and 133% obtained when samples were treated with EG1.