Peptone prepared from Hermetia illucens larvae: optimization of enzymolysis conditions and characteristics

Abstract:

[Background] Hermetia illucens (HI) used for the treatment of organic wastes such as kitchen waste is rich in amino acids and nutrients, serving as a high-quality and economical source of protein. [Objective] To prepare peptone with H. illucens larvae (HIL) for bacterial culture and provide a new idea for the application of HI. [Methods] Peptone was prepared from HIL by enzymolysis. The optimal enzymolysis conditions were determined by single factor tests, and the biochemical and functional properties of HIL-derived peptone and commercial tryptone were compared. Escherichia coli ATCC25922 was cultured with two peptone products and the growth kinetics was compared. [Results] The optimal conditions for preparing HIL-derived peptone were enzymolysis with the enzyme complex (trypsin:alkaline protease=1:1) added at 1.3% (mass fraction ) and at pH 7.0 and 54 ℃ for 4 h, under which the hydrolysis degree of defatted HIL was (19.34±0.15)%. The functional and biochemical properties showed no significant differences between HIL-derived peptone and commercial tryptone (P>0.05). The X_max,and λ of E. coli ATCC 25922 grown in the medium supplemented with HIL-derived peptone were 6.44 and 2.45, respectively, and those of E. coli ATCC 25922 grown in the medium supplemented with commercial tryptone were 6.14 and 3.19, respectively. The X_max,and λ showed no significant differences between HIL-derived peptone and commercial tryptone (p>0.05).[Conclusion] HIL-derived peptone can replace commercial tryptone as a component of the medium for culturing E. coli.