Improvement of xylitol production by Candida guilliermondii FTI 20037 previously adapted to rice straw hemicellulosic hydrolysate.
OBJECTIVE
To evaluate a simple and economical technique to improve xylitol production using concentrated xylose solutions prepared from rice straw hemicellulosic hydrolysate.


RESULTS
Experiments were carried out with rice straw hemicellulosic hydrolysate containing 90 g l-1 xylose, with and without the addition of nutrients, using the yeast Candida guilliermondii previously grown on the hydrolysate (adapted cells) or on semi-defined medium (unadapted cells). By this method, the yield of xylitol increased from 17 g l-1 to 50 g l-1, and xylose consumption increased from 52% to 83%, after 120 h of fermentation. The xylitol production rates were very close to that (0.42 g l-1 h-1) attained in a medium simulating hydrolysate sugars.


CONCLUSIONS
Yeast strain adaptation to the hydrolysate showed to be a suitable method to alleviate the inhibitory effects of the toxic compounds. Adapted cells of Candida guilliermondii can efficiently produce xylitol from hydrolysate with high xylose concentrations.


CONCLUSIONS
Yeast adaptation helps the bioconversion process in hydrolysate made from lignocellulosic materials. This low-cost technique provides an alternative to the detoxification methods used for removal of inhibitory compounds. In addition, the use of adapted inocula makes it possible to schedule a series of batch cultures so that the whole plant can be operated almost continuously with a concomitant reduction in the overall operation time.
Silva
C J
CJ
Department of Biotechnology/FAENQUIL, Rodovia Itajubá-Lorena, Lorena-SP, Brazil.
Roberto
I C
IC
D001709:Biotechnology / Q000379:methods; D001711:Biotransformation; D002175:Candida / Q000254:growth & development / Q000378:metabolism*; D015169:Colony Count, Microbial; D003470:Culture Media / Q000378:metabolism*; D005285:Fermentation; D006868:Hydrolysis; D012275:Oryza / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism*; D013997:Time Factors; D014993:Xylitol / Q000096:biosynthesis* / Q000191:economics / Q000378:metabolism
D003470:Culture Media; D011134:Polysaccharides; C007916:hemicellulose; D014993:Xylitol