Hemicellulosic hydrolysates production

When screening a large number of Lactobacillus strains for lactate production using hemicellulose hydrolysate, strains L. pentosus CHCC2355 and L. brevis CHCC2097 were selected and evaluated further (Garde et al, 2002). Each strain produced lactate with 88% (for L. pentosus) and 61% of the theoretical yield (L. brevis), respectively, from wheat straw hydrolysate without visible inhibition. The operation of the phosphoketolase pathway in these... 

Garde, A., Jonsson, G., Schmidt, A. S., and Ahring, B. K. 2002. Lactic acid production from wheat straw hemicellulose hydrolysate by Lactobacillus pentosus and Lactobacillus brevis. Bioresour. Technol., 81,217-223. 

The xylitol production rate is highest at very high xylose concentrations (80 g/1) [8, 10]. However, concentrating the hemicellulose hydrolysates using vacuum evaporation to achieve high xylose concentrations also concentrates the non-volatile inhibitors [11]. At these inhibitor concentrations, volumetric productivity actually declines [12-14]. Many studies have demonstrated the inhibitory effect of these hydrolysis-derived compounds on growth and production of products, such as ethanol and xylitol [15-16]. Concentrated hydrolysate requires detoxification for optimum xylitol production. 

The results of toxicity experiments performed using C. guilliermondii in batch fermentations are generally similar to that observed in other studies using semi-synthetic or actual hemicellulose hydrolysates for xylitol or ethanol production. Dominguez et al. 

Temperatures around 30 C have been utilized for xylitol production yeasts cultivated in synthetic medium or in hemicellulosic hydrolysates produced from... 

Jin P, Li S, Lu SG, Zhu JG, Huang H. (2011b). Improved 1,3-propanediol production with hemicellulosic hydrolysates (corn straw) as cosubstrate impact of degradation products on Klebsiella pneumoniae growth and 1,3-propanediol fermentation. Bioresource Technol, 102, 1815-1821. 

As cellulose only represents 30-40% of the lignocellulosic biomass, the utilization of only glueose in the fermentation would undeniably have an effect on the overall biomass to ethanol conversion yield. Therefore, it is necessary to eonsider the utilization of the hemicellulose hydrolysate in the development of the advanced generation bioethanol production process. ... 

Production of Fuel Ethanol from Hemicellulosic Hydrolysates... 

Nigam, J. N. (2001). Ethanol production from wheat straw hemicellulose hydrolysate by Pichia stipitis. Journal of Biotechnology, 87, 17—27. 

In another study, recombinant Escherichia coli TGI (pSYLlO ) harboring the Alcaligenes eutrophus PHA biosynthesis genes could efficiently produce P(3HB) from xylose and therefore potentially from low-cost hemicelluloses hydrolysate (Lee 1998). A P(3HB) concentration of 1.7 g L was obtained in a defined medium containing 20 g L xylose. P(3HB) production could be enhanced by more than twofold if a small amount of cotton seed hydrolysate or soybean hydrolysate was supplemented. The P(3HB) concentration, P(3HB) content, and P(3HB) yield on... 

Lopes M, Rocha R, Zanotto S, Gomez J, Silva L (2009) Screening of bacteria to produce polyhydroxyalkanoates from xylose. World J Microbiol Biotechnol 25(10) 1751-1756 Lopes MSG, Freire RKB, Chouman K, Gomez JGC, da Silva LF (2010) Engineered bacteria For PHB production from hemicellulosic hydrolysate. In International symposium on biopolymers, Stuttgart, p 72... 

Treatment with the enzymes peroxidase and laccase, obtained from the ligninolytic fungus Trametes versicolor, has been shown to increase the maximum ethanol productivity in a hemicellulose hydrolysate (Palmqvist and Hahn-Hagerdal, 2000). To detoxify phenolic inhibitors, laccase from T. versicolor was expressed in S. cerevisiae. The laccase expressing strain had the ability to convert coniferyl aldehyde at a faster rate than a control strain not expressing laccase, which enabled faster growth and ethanol fermentation in the presence of coniferyl aldehyde (Larsson et al., 2001). 

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