Fermentation performance, kinetics and mixed sugar utilization of Saccharomyces cerevisiae 2011 in sweet sorghum medium under unsterilized conditions.

Date

4-2009

Degree

Bachelor of Science in Chemical Engineering

College

College of Engineering and Agro-Industrial Technology (CEAT)

Adviser/Committee Chair

Catalino G. Alfafara

Co-adviser

Fidel Rey P. Nayne, Jr.

Committee Member

Rex B. Demafelis, Jovita L. Movillon

Abstract

Three initial inoculum levels [5%, 10%, and 20% (v/v)] of Saccharomyces cerevisiae 2011 were used to assess its performance during non-sterile fermentation using sweet sorghum syrup as medium in a 4.0-L bioreactor. The effects of initial inoculum concentration were related to the growth, substrate consumption, and ethanol production of the yeast being studied. In addition, the utilization of mixed sugars was also determined. The culture with 10% initial inoculum level had the highest specific growth rate (m) of0.21h⁻¹ during exponential phase. However, it only ranked 2ⁿᵈ in terms of ethanol productivity with respect to substrate consumption. While 10% had Yp/s=0.492, it was at 20%(Yp/s=0.602) that most of the sugar consumed were directly converted to ethanol. The results showed that having value for specific growth rate does not necessarily mean good ethanol production. Most of the carbon may be channeled more for cell production rather than for product formation (ethanol). For all the initial inoculum levels considered, the results showed that S. cerevisiae 2011 seem to prefer fructose over glucose and sucrose, and this could be attributed to the presence of other microorganisms that might have competed with the yeast for glucose. In terms of economics, 10% "rule of thumb" initial inoculum level is still recommended to use even in unsterilized media. The overall fermentation efficiency obtained for 10% was 91.1% while 91.4% was calculated for 20%. This increase in fermentation efficiency is not enough to compensate for the difference of the volume used for inoculation.

Language

English

LC Subject

Fermentation--Congresses, Fermentation, Yeast.

Location

UPLB College of Engineering and Agro-Industrial Technology

Call Number

LG 993.5 2009 E62 A48

Document Type

Thesis

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