Enhancement of microalgal production through bacterial mineralization of ethylene glycol

Abstract

Aim: In this study, ethylene glycol was supplied to an algal-bacterial consortium to investigate the effect of bacterial mineralization of ethylene glycol on algal growth. Methodology: Batch cultures of bacteria and Chlorella fusca monocultures, as well as algal-bacterial consortium were fed with 14,000 mg l-1 of ethylene glycol and incubated in one liter glass bottles at 25°C with light intensity of 300 μmol m-2 s-1 in a 12 hr-light:12 hr-dark cycle. A monoculture of C. fusca without ethylene glycol was also cultured under similar conditions to test algal growth inhibition. Results: In the consortium, there was more than 2-fold increase in the maximum algal specific growth rate and a 1.3-fold increase in the maximum bacterial specific growth rate. Furthermore, the maximum ethylene glycol removal efficiency by consortium was 89%, while those by bacteria monoculture was 31%. No apparent removal of ethylene glycol by the C. fusca monoculture was observed. Interpretation: The enhancement of microbial growth rates and ethylene glycol degradation in consortium compared to monocultures indicates that symbiotic relationship between algae and bacteria enhanced oxygen and CO2 exchange between them, as a result promoting growth and ethylene glycol degradation. This study demonstrated the possibility of an algal-bacterial system for the production of microalgal biomass by feeding organic wastes, such as ethylene glycol-containing wastewater.