TY - JOUR

T1 - Valorisation of waste cooking oil using mixed culture into short- and medium-chain length polyhydroxyalkanoates

T2 - Effect of concentration, temperature and ammonium

AU - Tamang, Pravesh

AU - Nogueira, Regina

N1 - Funding Information: We would like to acknowledge the Indian Council of Agricultural Research (ICAR), India, for supporting Mr. Pravesh Tamang for this research through the Netaji Subhas- ICAR International fellowship. We would like to thank Mr. Rahul Ramesh Nair (Institute of Sanitary engineering and waste management) and Mrs. Hannah Behnsen (Institut für Kunststoff und Kreislauftechnik) for the TGA and DSC analysis of the PHA samples.

PY - 2021/12/10

Y1 - 2021/12/10

N2 - The production of polyhydroxyalkanoates (PHAs) from waste cooking oil (WCO) by a mixed culture was investigated in the present study at increasing WCO concentrations, temperature and ammonium availability. The PHA production was done in two steps: in the first step, a mixed culture was enriched in PHA-accumulating bacteria from activated sludge in a sequencing batch reactor operated in a feast-famine mode and in the second step the PHA accumulation by the enriched mixed culture was assessed in a batch reactor. In the enrichment step, two substrates, WCO and nonanoic acid were used for enrichment and in the PHA accumulation step only WCO was used. It was not possible to enrich a mixed culture in PHA-accumulating bacteria using WCO as substrate due to the development of filamentous bacteria causing foam formation and bulking in the reactor. However, our results showed that the mixed culture continuously fed with nonanoic acid was enriched in PHA-accumulating bacteria. This enriched culture accumulated both scl- and mcl-PHA using WCO as substrate. The maximum PHA accumulation capacity of this mixed culture from WCO was 38.2% cdw. Increasing the temperature (30–40 ℃) or WCO concentrations (5–20 g/l) increased the PHA accumulation capacity of the mixed culture and the ratios of scl-PHA to mcl-PHA. The presence of ammonium increased PHA accumulation (21.9% cdw) compared to the complete absence of ammonium (5.8% cdw). The thermal characterization of the PHA exhibited the advantageous properties of both scl- and mcl-PHA, i.e., higher melting temperature (152–172 ℃) similar to scl-PHA and a lower degree of crystallinity (12%) similar to mcl-PHA. This is the first study to report the potential of open mixed culture to produce scl- and mcl-PHA from WCO and thus contributing to the understanding of sustainable polymer production.

AB - The production of polyhydroxyalkanoates (PHAs) from waste cooking oil (WCO) by a mixed culture was investigated in the present study at increasing WCO concentrations, temperature and ammonium availability. The PHA production was done in two steps: in the first step, a mixed culture was enriched in PHA-accumulating bacteria from activated sludge in a sequencing batch reactor operated in a feast-famine mode and in the second step the PHA accumulation by the enriched mixed culture was assessed in a batch reactor. In the enrichment step, two substrates, WCO and nonanoic acid were used for enrichment and in the PHA accumulation step only WCO was used. It was not possible to enrich a mixed culture in PHA-accumulating bacteria using WCO as substrate due to the development of filamentous bacteria causing foam formation and bulking in the reactor. However, our results showed that the mixed culture continuously fed with nonanoic acid was enriched in PHA-accumulating bacteria. This enriched culture accumulated both scl- and mcl-PHA using WCO as substrate. The maximum PHA accumulation capacity of this mixed culture from WCO was 38.2% cdw. Increasing the temperature (30–40 ℃) or WCO concentrations (5–20 g/l) increased the PHA accumulation capacity of the mixed culture and the ratios of scl-PHA to mcl-PHA. The presence of ammonium increased PHA accumulation (21.9% cdw) compared to the complete absence of ammonium (5.8% cdw). The thermal characterization of the PHA exhibited the advantageous properties of both scl- and mcl-PHA, i.e., higher melting temperature (152–172 ℃) similar to scl-PHA and a lower degree of crystallinity (12%) similar to mcl-PHA. This is the first study to report the potential of open mixed culture to produce scl- and mcl-PHA from WCO and thus contributing to the understanding of sustainable polymer production.

KW - Ammonium concentration

KW - Medium chain length (mcl)-PHA

KW - Mixed culture

KW - Temperature

KW - Thermal characterization

KW - Waste cooking oil

UR - http://www.scopus.com/inward/record.url?scp=85118587424&partnerID=8YFLogxK

U2 - 10.1016/j.jbiotec.2021.10.006

DO - 10.1016/j.jbiotec.2021.10.006

M3 - Article

C2 - 34688787

AN - SCOPUS:85118587424

VL - 342

SP - 92

EP - 101

JO - Journal of biotechnology

JF - Journal of biotechnology

SN - 0168-1656

ER -