Isolation and Identification of Local Ethanol Tolerant Yeast Populating Distillation and Milling Sites in Nigeria

Gidado Rose Suniso Maxwell

doi:10.11648/j.ajbio.20160405.11

Abstract

Two yeast strains referred to as OY and SY were isolated and characterised from local distillery and cereal milling sites. Isolation was done using potato dextrose media supplemented with 0.2% chloramphenicol. Morphological and biochemical results together with the rDNA internal transcribed spacer region (ITS) were identified as <i>Pichia kudriavzevii</i> strains GY1 and L9 respectively. OY and SY are ethanol tolerant strains, withstanding ethanol concentrations of up to 20% (v/v) in yeast extract, peptone, malt extract, glucose media. OY and SY displayed good growth in ethanol supplemented medium with pH ranging from 4.8-5.5 at 30°C. Growth measurements were determined by measuring optical density of the cells in broth using spectrophotometer at 570nm. The results obtained suggested that OY and SY demonstrated good parameters as ideal candidates for bioethanol production.

Highlights

The production of bioethanol through the conversion of reducing sugars such as glucose, sucrose and fructose by suitable microbial cells has seen explored for decades due to the numerous industrial applications of ethanol [1]
Alcoholic fermentation processes leads to a decrease in oxygen solubility as the process temperature increases, microbial involvement requires candidates that function under anaerobic conditions
Reports suggest that non-Saccharomyces yeasts like Candida sp., Hansenula sp., Kloeckera sp., Torulaspora sp., Kluyueromyces sp., Pachysolen tannophilus, Pichia stipitis and many more possess the ability to grow and participate in alcoholic fermentation [6], [7], [8]

Summary

Introduction

The production of bioethanol through the conversion of reducing sugars such as glucose, sucrose and fructose by suitable microbial cells has seen explored for decades due to the numerous industrial applications of ethanol [1]. Alcoholic fermentation processes leads to a decrease in oxygen solubility as the process temperature increases, microbial involvement requires candidates that function under anaerobic conditions. The preference for yeast over bacteria cells for ethanol production is due to the inherent ability of the former to withstand higher temperatures, grow at high osmotic pressure, yield higher levels of ethanol, etc [5]. Selection of new candidate yeast strains that can tolerate different levels of ethanol adds to the arsenal of microorganisms that can be manipulated for different industrially significant fermentation processes. Reports suggest that non-Saccharomyces yeasts like Candida sp., Hansenula sp., Kloeckera sp., Torulaspora sp., Kluyueromyces sp., Pachysolen tannophilus, Pichia stipitis and many more possess the ability to grow and participate in alcoholic fermentation [6], [7], [8]

Objectives

Methods

Results

Conclusion