Date of Publication

9-2011

Document Type

Master's Thesis

Degree Name

Master of Science in Chemical Engineering

Subject Categories

Chemical Engineering

College

Gokongwei College of Engineering

Department/Unit

Chemical Engineering

Thesis Adviser

Joseph Auresenia
Josephine Q. Borja

Defense Panel Chair

Pag-asa D. Gaspillo

Defense Panel Member

Cynthia Fabian
Dennis Yu

Abstract/Summary

In this study, forty isolates were extracted from soil collected near ethanol distillation columns that are exposed to high temperature and high ethanol concentration condition by isolating on Yeast Peptone Dextrose (YPD) agar plate supplemented with 0.5 g/l chloramphenicol as antibacterial agent. In order to obtain yeast strains that could tolerate both high temperature and high ethanol concentration, the isolated yeast strains were screened for their ability to grow under high ethanol concentration (0% - 10%, v/v) and high temperature conditions (35 oC - 50 oC) in agar plate. All the strains grew in YPD agar plates at 35 oC containing 0% to 10% (v/v) ethanol concentration and 45 oC without ethanol addition but no strains at 50 oC. Only eight strains were able to grow up to 43 oC in YPD agar plates containing 10% (v/v) ethanol concentration. Eight strains were then selected and screened for ethanol fermentation ability in a liquid medium containing 20% (w/v) glucose at 40 oC. Only four strains that produced high ethanol concentration were selected and submitted to two acclimatization treatments. Progressive acclimatization of the yeast strains were conducted in the YPD liquid medium in two (phases): the first from 0% to 16% (v/v) ethanol concentrations perform in seven steps at 35 oC, and the second from 40 oC to 50 oC in four steps. The results showed that all the yeast strains could grow in the medium containing up to 4% exogenous ethanol at 35 oC and up to 40 oC without ethanol addition. Thermal shock and ethanol shock acclimatization were carried out at different temperature, such as 35 oC, 40 oC, 45 oC, 50 oC, and different ethanol concentration, such as 0%, 2%, 4% and 6% (v/v). The influence of temperature and initial ethanol addition on cell activities and ethanol production were investigated. A high temperature led to a decrease in the ethanol and cell yields but an increase in the inhibition effect of ethanol on cell growth and ethanol production. The effect of temperature on the kinetic behavior of all tolerant strains was also investigated at temperature from 35 oC to 40 oC, using glucose and brown sugar as the substrate. Three state variables, biomass, ethanol and the iii De La Salle University substrate were used to describe the phenomenon. The following results were obtained: the maximum specific growth rate (µm) and the ethanol inhibition term on cell growth (Pm) slightly changed with temperature increase from 35 oC to 40 oC for using glucose as substrate. On the other hand, the fermentation with the brown sugar as substrate, both µm and Pm further decreased with increases of temperature. The kinetics of ethanol fermentation at temperatures 35 oC and 40 oC can be simulated fairly well with the proposed model. The results from the batch cultivation showed that the tolerant strain S109 produced high concentration of ethanol at both 35 oC and 40 oC in glucose and brown sugar medium. Ethanol production by this strain in shaking flask cultivation at 35 oC and 40 oC using glucose medium was 6.25 % and 5.85 % (w/v) ) of ethanol, respectively, while this for brown sugar medium was 7.79 % (w/v) ) of ethanol at 35 oC. This strain was then tested for their fermentation ability in continuous ethanol production system using brown sugar as substrate. The continuous stirred tank reactor (CSTR) was carried out in 4-liters flask at 40 oC for 120 h with 20% (w/v) of total sugar. Under these conditions, the ethanol yield, productivity and theoretical yield of strain S109 was 0.455 g g-1, 0.56 g l-1 h-1 and 89.11%, respectively.

Abstract Format

html

Language

English

Format

Electronic

Electronic File Format

MS WORD

Accession Number

CDTG005072

Shelf Location

Archives, The Learning Commons, 12F Henry Sy Sr. Hall

Physical Description

184 leaves : ill. ; 1 computer optical disc

Keywords

Ethanol; Yeast

Upload Full Text

wf_yes

Download

Share

COinS