Growth Profiles and Ethanol Production of Two Yeast Strains Kluyveromyces Marxianus Ifo-288 and Kluyveromyces Marxianus Ifo-617 during Fermentation of Soybean Pulp Hydrolyzate Substrates

Abstract

Two yeast strains, K.marxianus IFO-288 and K.marxianus IFO-617, were observed to utilize carbon and nitrogen sources obtained from enzymatically hydrolyzed soybean pulp (hydrolyzate). Under aerobic condition where 1.5% hydrolyzate was used, the maximum biomass of the two yeast yield reached 30% with the protein contents of 47-53%. The two yeast strains also fermented the soybean pulp hydrolyzate and produced alcohol when anaerobic condition was set. The alcohol production effi ciencies of the K. marxianus IFO-288 and K. marxianus IFO-617were 49% and 59.7%, respectively in the medium containing 1.5% hydrolyzate. These values were noticed to decrease for the two strains when the concentration of the hydrolyzate was increased. At the concentrations of 2.5% and 5% hydrolyzate for examples, the alcohol production effi ciencies of the K.marxianus IFO-288 became 42.5% and 18.5%, respectively, while 45.6% and 20.8%, respectively were recorded in the medium inoculated with K. marxianus IFO-617. At 10% hydrolyzate concentration, none of the yeast strains grew or produced alcohol, indicating that some inhibitory substances in hydrolyzates were present in the fermentation medium.