Isolation and identification of gut bacteria from Vespa mandarinia Smith and screening of digestive enzyme-producing strains

Abstract:

[Background] Vespa mandarinia Smith can control a variety of field pests and has medicinal values. The structure and function of gut bacteria in V. mandarinia remain to be studied. [Objective] To obtain the culturable bacteria from the gut of V. mandarinia and screen out the bacterial strains capable of producing digestive enzyme, so as to provide a basis and research materials for understanding the influence of gut bacteria on the host and for utilization of the functional bacterial strains. [Methods] The gut bacteria of V. mandarinia were isolated by the culture method, and 16S rRNA gene sequencing was employed to identify the strains. Halo-forming method was adopted to screen out the strains producing protease, lipase, amylase, and cellulase, and the ratio of halo diameter (D) to bacterial colony diameter (d) was used to compare the strain capability of producing digestive enzymes. [Results] A total of 10 species of bacteria belonging to 6 genera were isolated from the gut of V. mandarinia, including 5 species of Bacillus, 1 species of Enterococcus, Staphylococcus, Leuconostoc, Lactococcus, and Acinetobacter, respectively. Six strains producing digestive enzymes were screened out from the 61 strains obtained. Among them, B. thuringiensis V44 had the ability to produce protease, amylase, lipase, and cellulase. E. faecalis V6 was capable of producing amylase, protease, and lipase. B. cereus V43 can produce protease, amylase, and cellulase. E. faecalis V20, B. cereus V19, and B. wiedmannii V22 demonstrated the ability to produce protease. [Conclusion] The gut bacteria resources of V. mandarinia were abundant, and some strains were capable of producing digestive enzymes, which can facilitate the digestion and affection of health of V. mandarinia. All the 6 strains screened out in this study could produce protease. Strains V43 and V44 showed the strongest ability to produce amylase and lipase, respectively, which could be further developed as gut functional strain resources.