Enhancing algal biomass and lipid production by phycospheric bacterial volatiles and possible growth enhancing factor

Abstract

The concept of sustainable biodiesel production using microalgae has attracted a lot of attention as an emerging green energy technology. However, low algal biomass and lipid productivity hinder cost-effective biodiesel production. To overcome these problems, this study examined the effect of bacterial volatile compounds (VCs) on the growth and lipid production of microalga Chlorella vulgaris OW-01. The VCs of phycospheric bacteria including Hyphomonas sp., Rhizobium sp., and Sphingomonas sp. efficiently augmented algal biomass in a newly developed VCs experimental apparatus. Moreover, an apparent increase in total lipid content along with a 2.34-fold increase in productivity was observed in Hyphomonas sp. VCs？exposed algal biomass. Fatty acid methyl esters (FAME) composition also demonstrated that the algal biodiesel properties were somewhat modified by exposure to bacterial VCs. A LiOH filter-inducing CO2-removed bacterial VCs (CRBVCs) also enhanced daily growth of microalgae, as compared to the control culture (aeration), indicating that CRBVC included growth-promoting volatiles. Of those factors, volatile indole was identified as a possible algal growth enhancing factor, and it showed a higher growth-promoting effect than dimethyl disulfide and dimethyl trisulfide. Based on these results, it is speculated that the use of bacterial VCs for algal cultivation is a promising future bioprocess for the algal biomass and biodiesel production.