Isolation of bacteria that decompose major polysaccharides in the cell wall of the marine red alga Porphyra yezoensis and their application for protoplast production

Abstract

We attempted to screen for bacteria that could decompose major polysaccharides in the cell wall of the marine red alga Porphyra yezoensis from Porphyra-culturing farms to enable simple and high-yield preparation of protoplasts with the crude enzyme from a single bacterial origin. A total of 275 positive bacterial strains were isolated by enrichment culture supplemented with Porphyra powder or xylan. Nine strains were capable of producing protoplasts from Porphyra thalli in a 10-fold concentrated culture broth. These strains were identified as two Flavobacterium spp., one Alteromonas sp., four Acinetobacter spp., and two Vibrio spp. The crude enzymes of these bacteria could release 106 protoplast cells from 0.1 g of Porphyra thalli. The crude enzyme from Alteromonas sp. strain ND137 produced the most protoplasts among the nine strains tested. Moreover, an assay of the crude enzymes from the nine bacterial strains for glycosidase activity against four major polysaccharides (xylan, mannan, porphyran, and cellulose) of P. yezoensis revealed strong decomposing activity against these polysaccharides. Xylanase activity was highest in these glycosidases, suggesting that xylanase might be a very important factor in producing protoplasts from Porphyra thalli.Key words: Porphyra, cell wall, bacteria, decomposing polysaccharide.