Construction of artificial symbiotic community using Chlorella-symbiont association and it's application

点击翻译按钮获取中文摘要

Chlorella sorokiniana IAM C-212 has long been maintained in slant culture as a mixed strain, representing an associated natural microbial consortium. The consortium was separated and four nonalgal constituents, a fungal strain (Acremonium sp.), and three bacterial strains (Ralstonia pickettii, Sphingomonas sp. DD38, Microbacterium trichotecenolyticum) were isolated and identified. The interaction between Chlorella and its symbionts under photoautotrophic conditions involved both mutualism and commensalisms. Sphingomonas sp. And M. trichotecenolyticum were harbored on the sheath produced by Chlorella, while Acremonium sp. And R. pickettii directly adhered to the Chlorella cell surface by using lectin-like substances. The sheath is composed of sugars, amino acids, vitamins and metals. A novel artificial medium that imitates photoautotroph-heterotroph interaction was developed. With the artificial medium, it was possible to selectively isolate some novel bacterial strains. The sheath is a suitable habitat for several symbiotic microorganisms because it ensures close proximity between the C. sorokiniana and symbionts. The sheath was increased by addition of calcium chloride. The sheath resulted in coflocculation of C. sorokiniana and the associated symbiotic bacteria, thus strengthening the bacterial-Chlorella symbiotic association. An application of this technique was demonstrated by constructing a complex of C. sorokiniana and a propionate-degrading bacterium (PDS1). Although propionate inhibited the growth of axenic C. sorokiniana, the C. sorokiniana-PDS1 complex (CPC) showed good growth in a medium containing a high concentration of propionate. The CPC was also used for simultaneous removal of organic acids, nitrate, ammonia and phosphate.