Enzyme Production for Enriching Protein from Soy Meal as Aquaculture Feed

Global demand for aquaculture seafood is growing rapidly. Fishmeal is the conventional protein source for aquaculture feed but fishmeal production has long reached the maximum sustainable capacity. Alternative protein sources are required. Soy meal contains predominantly protein (~53%) and carbohydrate (~32%). It is a good potential substitute but needs protein enrichment (to > ~70% as in fishmeal) and removal of indigestible carbohydrate. We have developed an enzymatic process for meeting both requirements and produced good enzyme mixtures for this purpose. Enriched soy protein can be easily from hydrolysate. Containing hydrolyzed carbohydrate, the hydrolysate can be used as fermentation substrate for producing other value-added products such as arabitol. We have selected strains and studied effects of medium and fermentation conditions on enzyme productivity and blend of enzyme activities. Activities of 7 enzyme groups, i.e., cellulase, xylanase, pectinase, polygalacturonase, a-galactosidase, protease, and sucrase, were analyzed; direct soy meal processing tests were conducted to compare concentrations of released reducing sugar and total carbohydrate. Optimal activity ratios of different enzyme groups were established from extensive hydrolysis experiments and modeling. The knowledge is guiding further optimization of fermentation design and control.