Comprehensive study on volatile fatty acid production from Ettlia sp residue with molecular analysis of the microbial community

Abstract

The conversion of lipid extracted microalgal residues (LE mu ARs) into renewable energy provides a promising route for microalgal biodiesel production for various industries. In this study, volatile fatty acid (VFA) production and soluble chemical oxygen demand (SCOD) from the LE mu AR of the green algae Ettlia sp. was optimized with the response surface methodology (RSM) varying the temperature from 25 to 65 degrees C and the food to microorganism ratio (F/M ratio) from 0.5 to 2.5 as the independent variables. A F/Mratio of 1.76 (g COD/g VSS) and temperature of 47.97 degrees C was found to be the optimal condition. Though the fit was rather lacking, the p-value was sufficiently significant at 1% alpha level validating the optimization model. Additionally, next generation sequencing (NGS) indicated significant correlations between VFA and its microbial community, revealing that an anaerobic bacterium species, Sporanaerobacter acetigenes, was a dominant VFA producer. This study shows that VFA production could indeed be a viable direction that would make the microalgae-based biofuel production competitive. (C) 2016 Elsevier B.V. All rights reserved