Alcohol production from starch by mixed cultures of Aspergillus awamori and immobilized Saccharomyces cerevisiae at different agitation speeds.
The influence of different agitation speeds on alcoholic fermentation by free and immobilized cells of Saccharomyces cerevisiae in a co-culture with free cells of Aspergillus awamori was investigated. Starch hydrolysis and glucose, glucoamylase and alpha-amylase accumulation in the fermentation medium was affected by agitation speed. Maximum amounts of the enzymes were obtained at 150-200 rpm after 72 h where, maximum growth and glucose accumulations were noticed at 200-300 rpm. Alcohol production was stimulated by low agitation speed (50 rpm) and decreased at higher speeds. The results also showed that the amount of produced alcohol was affected by the time of yeast inoculation. When the inoculation of yeast was carried out after the growth of fungi for 72 h, the amounts of produced alcohol increased by 84, 75, 89 and 68% at 50, 100, 150 and 200 rpm, respectively than that produced when the two organisms were inoculated together at the beginning of the fermentation process. A batch culture of the two organisms produced about 2% (v/v) alcohol from 12% (w/v) corn starch in 72 h at 50 rpm. On the other hand, the immobilized yeast and suspended A. awamori produced more alcohol reaching 3.7% (v/v) at 200 rpm under the same cultivation conditions. The fermentation process was less affected by alginate and cell concentrations of the immobilized yeast. Repeated batch fermentation by co-culture of A. awamori and immobilized yeast cells were successfully used for 12 times without a significant loss in alcohol production.
Farid
M A
MA
Natural and Microbial Products Department, National Research Centre, Tahrir Street, Dokki, Cairo, Egypt. nrcfarid@yahoo.com
El-Enshasy
H A
HA
Noor El-Deen
A M
AM
D000464:Alginates; D001230:Aspergillus / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D018914:Cells, Immobilized; D003470:Culture Media; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005087:Glucan 1,4-alpha-Glucosidase / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D007218:Industrial Microbiology / Q000379:methods; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D013213:Starch / Q000378:metabolism*; D000516:alpha-Amylases / Q000378:metabolism
D000464:Alginates; D003470:Culture Media; D006603:Hexuronic Acids; D000431:Ethanol; D020723:Glucuronic Acid; D013213:Starch; D000516:alpha-Amylases; D005087:Glucan 1,4-alpha-Glucosidase; D005947:Glucose