The Enrichment of Microbial Community for Accumulating Polyhydroxyalkanoates Using Propionate-Rich Waste

Bo Wu, Dan Zheng, Zheng Zhou, Jing-Li Wang, Xiao-Lan He, Zheng-Wei Li, Hong-Nan Yang, Han Qin, Min Zhang, Guo-Quan Hu, Ming-Xiong He

Polyhydroxyalkanoates (PHAs) are promising alternatives to plastics since they have similar properties to polyolefin but are biodegradable and biocompatible. Recently, the conversion of propionate wastewater to PHAs by undefined mixed microbial cultures becomes attractive. However, how microbial community changes remains unclear during the enrichment step, which is critical for a robust PHA-producing system. In this study, PHA-accumulating cultures were enriched under feast/famine condition using propionate-rich substrates. Our results showed that during the first 2 h of the enrichment, dissolved oxygen of cultures increased remarkably until saturation, and amounts of C, N, and chemical oxygen demand of cultures decreased significantly to a very low level. High-throughput sequencing revealed that bacterial populations affiliated with Alphaproteobacteria and Bacteroidetes dominated the cultures enriched. Most of these dominant populations contributed to the conversion of short-chain fatty acids to PHAs. Being fed with the substrate rich in propionate but without nitrogen, the cultures enriched could accumulate nearly 27% PHAs at 72 h with higher content of hydroxyvalerate. Our work reveals the process in which environmental microbes responded to propionate-rich condition and shifted to populations for accumulating PHAs; it also will be helpful to develop an efficient PHA-producing system using propionate-rich waste.