Effects of autolysis and hydrolysis of bacterial protein meal grown on natural gas on chemical characterization and amino acid digestibility

Bacterial protein meal produced from bacteria cultured on natural gas is a novel alternative protein source. Several products with different nutritional features were made from basic bacterial protein meal (BBP) by autolysis and hydrolysis. These products were investigated in terms of chemical characterization of the protein fraction and amino acid digestibility, using mink as model animal. The BBP, autolysate, autolysate extract, hydrolysate extract, and the insoluble byproducts of the latter two exhibited considerable differences in amino acid profile and great differences in protein solubility and molecular size. Apparent digestibility of arginine, lysine and methionine was high in all products, while cysteine digestibility was low. Compared to BBP, the extracts of autolysate and hydrolysate showed higher digestibility of most amino acids. All products of autolysis showed higher tryptophan digestibility but lower cysteine digestibility compared to BBP. The byproducts from autolysate and hydrolysate with low protein solubility and large molecule size had lower amino acid digestibility than the extracts. Autolysis and hydrolysis and separation into extracts of high protein solubility and small molecular size increased amino acid digestibility of the bacterial protein.