Polyhydroxyalkanoate production using two‐stage continuous stirred tank activated sludge systems with glycerol as a carbon source

Abstract

BACKGROUND Polyhydroxyalkanoate (PHA) is a biopolymer that can be used as a biodegradable plastic. The incorporation of PHA production into wastewater treatment processes is a promising strategy for resource recovery. This study investigated PHA production in two‐stage continuous stirred tank reactor (CSTR)‐activated sludge (AS) systems fed with synthetic wastewater containing glycerol. The effects of the hydraulic retention time (HRT) ratios of the first and the second stages, which reflects the feast/famine ratio, at 0.04, 0.15, and 0.33 were examined. RESULTS The PHA accumulation and PHA consumption patterns under feast/famine conditions were successfully achieved in systems operated at HRT ratios of 0.04, 0.15, and 0.33 with influent glycerol concentrations of 3000 mg COD/L. Then, the sludge from these systems was tested for PHA accumulation in fed‐batch reactors. Maximum PHA contents of 21.8 wt%, 13.1 wt%, and 8.7 wt% were obtained for the sludge from the systems operated at HRT ratios of 0.04, 0.15, and 0.33, respectively. From the microbial community analysis via 16S rRNA gene amplicon sequencing (MiSeq, Illumina), the relative abundance of betaproteobacteria decreased, whereas the relative abundances of alphaproteobacteria and gammaproteobacteria increased after cultivation in the two‐stage CSTR AS systems. CONCLUSION The highest PHA accumulation was achieved at the lowest HRT ratio of the first and the second stages in the two‐stage CSTR AS systems. This study serves as an example of integrating PHA production into wastewater treatment systems, which enables us to apply the concept of resource recovery from wastewater. © 2019 Society of Chemical Industry

Biotransformation of oleochemical industry by‐products to polyhydroxyalkanoate bioplastic using microbial fermentation: A review

“…Additionally, optimization with response surface methodology had produced 64 wt% of PHA from Burkholderia cepacia BPT1213 using waste glycerol (Zain et al., 2020). Most literature to date reporting substantial PHA conversion from glycerol had elucidated the use of super PHA producers, fermentation optimization, and innovative strategies (i.e., mixed cultures), thus implying the need for future research efforts towards parameter modification, novel technique advancement, and environmental isolation or genetic recombination (Heepkaew & Suwannasilp, 2020; Kourmentza et al., 2019; Li et al., 2020; Paula et al., 2019; Pereira et al., 2019). However, PHA yield is apparently varied even among bacterial strains despite being of the same species or genus, which signifies a comparable prominence to comprehensively understand and engineer the biosynthetic pathway ( Exhibit 6 ).…”