H. Sivaraman et al., EFFECT OF SYNTHETIC ZEOLITE ON ETHANOLIC FERMENTATION OF SUGARCANE MOLASSES, Enzyme and microbial technology, 16(8), 1994, pp. 719-722
Synthetic zeolites such as Silicalite have been shown to act as accele
rators of fermentation of sugarcane molasses to ethanol by Saccharomyc
es cerevisiae. Silicalite added at 1 gl(-1) increased initial specific
ethanol productivity in the fermentation of sugarcane molasses to eth
anol at all concentrations of the substrate in the range of 100-300 gl
(-1) total sugars. Increasing the additive level up to 30 gl(-1) did n
ot enhance further the initial rates of conversion. However, with the
accumulation of inhibitory levels of the product in the later phase of
fermentation of high-gravity molasses, marked enhancement in the rate
of conversion was observed at the higher level of 20 gl(-1) of Silica
lite supplementation compared to the effect observed with 1 gl(-1). At
the highest concentration of 300 gl(-1) of total molasses sugars, 130
gl(-1) product concentration was obtained in about 48 h, indicating a
bout 95% conversion in the presence of 2% of the zeolite, while in the
absence of the additive the product concentration leveled off at 120
gl(-1), attained in a period of about 72 h. Fermentation of molasses i
n semibatch mode at 150 gl(-1) total sugar concentration in the presen
ce of 20 gl(-1) Silicalite resulted in uniformly enhanced conversion r
ates compared to fermentation in the absence of the additive. The peri
ods required for completion of fermentation were about 16h in the pres
ence of Silicalite and about 24 h in the absence of the zeolite in all
the 10 cycles of use tried. The probable modes of action of Silicalit
e as an accelerator of the ethanolic fermentation of molasses through
removal of inhibitory substances and changes in the flocculation behav
ior of the yeast are discussed.