Isolation and characterization of enzyme-producing bacteria of the silkworm larval gut in bioregenerative life support system

• Differences of silkworm gut microbes under BLSS rearing and traditional rearing ways.
• Cellulase and amylase producing bacteria were separated in both rearing ways.
• Enterococcus, Erwinia and Pantoea are cellulase and amylase producing isolates in BRW.
• The isolates can be developed into probiotics for improving animal protein in BLSS.

Silkworm (Bombyx mori L.) larvae were used as an ideal animal protein source for astronauts in bioregenerative life support system (BLSS). Here, we compared the differences in bacterial communities of the silkworm larval gut and cellulase-producing and amylase-producing bacteria between the BLSS rearing way (BRW) and the traditional rearing way (TRW) through Illumina Miseq sequencing, culture-dependent approach, 16S rDNA and ITS sequencing, phylogenetic analysis to find the role of gut bacteria in food digestion. The analysis of Miseq showed that the gut microbiota in the BRW was significantly changed than that in the TRW. Results revealed that the isolates can produce cellulose-degrading and starch-degrading enzymes of gut bacteria of silkworm in the BRW which decreased compared with that of the TRW, but the number of isolates both secrete cellulase and amylase are equal. The isolates that can produce both enzymes in the TRW were Alternaria sp. Preussia sp and Coprinellus radians. Meanwhile, in the BRW we found Enterococcus, Erwinia and Pantoea can produce cellulase and amylase. We could use the dominant populations to make probiotic products for nutrient absorption and disease prevention in BLSS to improve gut microecology, as well as the yield and quality of animal protein.