Effects of pH and Aeration Conditions on Xylitol Production by Candida and Hansenula Yeasts

Zoltán Mareczky,Csaba Fehér,Zsolt Barta,Katalin Réczey,Anikó Fehér

doi:10.3311/ppch.8116

Abstract

During the fermentative production of xylitol the following environmental parameters have a controlling effect on the xylitol yield: concentration of monosaccharides, temperature, aeration and pH. The purpose of the present work was to evaluate xylitol production by four yeast strains at different pH values and oxygen transfer rates (OTRs). The highest xylitol yields were obtained under the following conditions: Candida parapsilosis: pH 5.0, OTR 6.1 mmol L-1 h-1; Candida guilliermondii: pH 4.5, OTR 5.7 mmol L-1 h-1; Candida boidinii: pH 6.0, OTR 5.7 mmol L-1 h-1; Hansenula anomala: pH 4.5, OTR 2.8 mmol L-1 h-1 using 50 g L-1 initial xylose concentration.

Highlights

Xylitol, a natural five-carbon sugaralcohol, has attracted attention because of its wide variety in use and its good biological impacts [1,2]
The purpose of the present work was to evaluate xylitol production by four yeast strains at different pH values and oxygen transfer rates (OTRs)
The highest xylitol yields were obtained under the following conditions: Candida parapsilosis: pH 5.0, OTR 6.1 mmol L-1 h-1; Candida guilliermondii: pH 4.5, OTR 5.7 mmol L-1 h-1; Candida boidinii: pH 6.0, OTR 5.7 mmol L-1 h-1; Hansenula anomala: pH 4.5, OTR 2.8 mmol L-1 h-1 using 50 g L-1 initial xylose concentration

Summary

Introduction

A natural five-carbon sugaralcohol, has attracted attention because of its wide variety in use and its good biological impacts [1,2]. Its sweetness is equal to sucrose, xylitol is used increasingly as a sweetener and it has anticariogenic attribute [3]. Xylitol raises the blood sugar level less than sucrose, and it can be used as an insulin-independent carbohydrate source for diabetics [4,5,6]. Xylitol is naturally present in some fruits and vegetables (e.g. cauliflower or cabbage lettuce) [10], its low concentration in plants makes production by extraction difficult and uneconomical [1]. Xylitol has been manufactured by catalytic hydrogenation of D-xylose using e.g. Raney nickel catalysts, and this requires expensive purification, in which D-xylose is separated from the other sugars obtained in the acidic hydrolysis of plant hemicelluloses [11,12]

Objectives

Methods

Findings

Conclusion