مرضیه شمعی

Xylitol is a naturally five – carbon polyol with a high sweetening power. Xylitol is the sweetest among the polyalcohols. The biotechnological method of producing xylitol by microorganisms has been studied as an alternative to the chemical method and is very environmentally safe. Xylitol is an attractive sugar substitute for use in the food-processing, nutritional supplement and pharmaceutical industries. Among the microorganisms, yeasts are considered as the best xylitol producer. The purpose of this study was xylitol production by Debaryomyces hansenii that isolated from pollen of Malva sylvestris flower. This strain was identified by 18SrRNA sequencing and following its alignment with existed similar strains in data bases. Xylitol was produced in production medium contained xylose and other compounds. Xylitol was first identified by thin layer chromatography (TLC) method then it was confirmed by Megasyme kit. Xylitol concentration was quantified using high performance liquid chromatography ( HPLC) method. This strain produced 20.45 g l-1 xylitol after 48 hours culture incubation in medium contained 40 g l-1 xylose.

Sorbitol is a 6- carbon polyol, which is used in food industries as a precursor for production of many products due to its sweetness and high solubility. The application of microbial process for sorbitol production has recently been becoming of point of interest because of requirement for suitable fermentative conditions, being cost effective and less environmental pollutions. The purpose of this study was to produce sorbitol from sucrose by Debaryomyces hansenii isolated from the nature.
The sorbitol producing yeast strain was isolated in a medium containing 40% glucose and 1% yeast extract. Following identification of yeast using ITS gene sequencing, we focused on the process of fermentation and production of sorbitol from sucrose. The quality and quantity of sorbitol production was analyzed by thin layer chromatography, colorimetric method and Megazime kit.
The sorbitol producing yeast strain was isolated from pollen of Malva sylvestris flower, and was identified as D. hansenii. This strain produced 5.23 g l-1 sorbitol after 5 days in medium containing of 150 g l-1 sucrose.
In this study sorbitol was produced by a D. hansenii isolated from the nature. Due to high efficiency of sorbitol production from sucrose by yeast, isolation of sorbitol producing native yeasts and optimization of the production conditions can be helpful for increases in quality and quantity of sorbitol production.