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Biotransformation Of Xylose Rich Corncobs to Xylitol By Fermentation

Avinash, Sinha (2005) Biotransformation Of Xylose Rich Corncobs to Xylitol By Fermentation. [Student Project Report]

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Abstract

This Dissertation / Report is the outcome of investigation carried out by the creator(s) / author(s) at the department/division of Central Food Technological Research Institute (CFTRI), Mysore mentioned below in this page.

Item Type: Student Project Report
Additional Information: This project is aimed at microbial production of xylitol, a sugar alcohol from xylose. Corncob has been selected as a source of xylose, as it is economically available, has high xylose concentration and its relatively high density makes its transport and storage easier. In this project, development of a process for microbial production of xylitol is attempted. Based on earlier experiments, Pichia farinosa has been selected as the yeast for conversion of xylose to xylitol. Optimization of hydrolysis of corncobs to give xylose, fermentation media & process parameters (i.e. pH, DO, Temp, Batch time) and downstream processing are worked out. The conditions for hydrolysis of corncobs have been optimized. Over liming of hydrolysate has been tried out and has proved to be effective in reducing time for xylitol production to 41 h from an average of 55 h. Activated charcoal treatment has been successful in de-colorization of hydrolysate. Nine fermentation trials were conducted. Batch volumes varying from 10 to 13 L in fermentor have been conducted. The maximum xylitol concentration and yield obtained using corncob hydrolysate are 3.68 g/L in 40-50 hours and 0.34 g xylitol/ g xylose respectively. Substitution of pharma media with yeast extract in three batches has shown to considerably minimize foaming problems. A yield of 0.51 g xylitol/ g xylose and maximum xylitol concentration of 12.05 g/L was obtained using pure xylose. Six shake flask experiments were conducted. These experiments were conducted with the following objectives: (1) to find the osmotolerance of yeast Pichia farinosa (2) affect of high initial xylose concentration on xylitol production and yield (3) affect of removal of inhibitors from corncob hydrolysate (4) influence of extra cellular metabolites released by the yeast on fermentation (5) feasibility of addition of ethanol during fermentation as a regenerator of critical cofactor NADPH for xylitol production. Downstream processing has been tried. In a series, centrifugation, microfiltration, ultrafiltration, activated charcoal de-colorization were used for processing the fermentation broth. The processed broth was concentrated under vacuum to get a maximum xylitol concentration of 46.53 g L-1. Crystallization has not yet been successful.
Uncontrolled Keywords: Xylitol, Xylose, Fermentation, Downstream processing, Media optimization
Subjects: 500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 31 Sugar Chemistry
600 Technology > 05 Chemical engineering > 04 Fermentation Technology
500 Natural Sciences and Mathematics > 07 Life Sciences > 04 Microbiology
Divisions: Fermentation Technology and Bioengineering
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 22 Dec 2006
Last Modified: 28 Dec 2011 09:26
URI: http://ir.cftri.com/id/eprint/367

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