Development of an ideal starch saccharification process using amylolytic enzymes from thermophiles.

The extensive efforts to screen thermophilic fungi and bacteria, isolated from various environmental samples, have resulted in the selection of Thermomucor indicae-seudaticae, Geobacillus thermoleovorans NP33 and G. thermoleovorans NP54 for the production of glucoamylase, amylopullulanase and alpha-amylase, respectively. Submerged and solid-state fermentation processes were optimized for maximizing the secretion of glucoamylase by T. indicae-seudaticae. The production of amylopullulanase and alpha-amylase by NP33 and NP54 in submerged fermentation was also optimized. Glucoamylase was optimally active at pH 7.0 and 60 degrees C and was shown to saccharify soluble as well as raw starches. Amylopullulanase and alpha-amylase exhibited optima at pH 7.0 and 100 degrees C and saccharified starch efficiently. Differential inhibition and action on mixed substrates clearly suggested that there are two separate active sites for alpha-amylase and pullulanase activities of amylopullulanase. Both alpha-amylase and amylopullulanase are high maltose-forming and Ca(2+)-independent. These amylolytic enzymes have been shown to be useful in starch saccharification alone and in combination.