Growth promotion of Chlorella vulgaris by modification of nitrogen source composition with symbiotic bacteria, Microbacterium sp. HJ1

Abstract To increase algal growth in treated livestock waste water, we designed a culture system targeting symbiotic bacteria. Microbacterium sp. HJ1 is a symbiotic bacteria associated with Chlorella vulgaris , which was found to increase the growth rate when controlled by nitrogen addition. The validated analysis model for nitrogen source mixture was used to analyze the growth and final pH of Microbacterium sp. HJ1, in different compositions of nitrogen sources, by elucidating the functions of each nitrogen ions such as NO 3 − , NO 2 − , and NH 4 + . By modifying the growth medium made from treated livestock waste water with additional nitrogen source, we were able to increase dry cell weight (DCW) of C. vulgaris by 65.7% and chlorophyll a contents by 78.8%. This is an example of an indirect method to increase algal biomass by changing the population of symbiotic bacteria, and it is the practical application of positive effects from symbiotic bacteria to the host.