Optimization of SSF for invertase activity using pressmud
was attempted in these studies. Tray no 2 holding
10% spent yeast and nutrient mix added to pressmud,
had shown higher specific enzyme activity (373.2 U/mg
at 72 h; Table 1). There is a preferred release of more invertase
with spent yeast samples in the pressmud milieu
compared to the cultured yeast (Table 1). The membrane
changes that would have taken place when present
in the ethanol rich medium for prolonged periods and
such stress filled ethanol production milieu would have
made the spent yeast cells more susceptible to the
stimulation from the SSF culturing on pressmud. There
are reports of enzymes getting released from microbial
cultures (when grown on solid substrates) as extracellular
enzymes which otherwise were intra cellular when grown
in liquid cultures (Lekha and Lonsane 1994; Mitchell and
Lonsane 1992). Lonsane and Ghildyal (1992) reported this
sort of stimulated release with glucose oxidase and invertase
earlier.