Bioconversion of biphenyl to a polyhydroxyalkanoate copolymer by Alcaligenes denitrificans A41

Abstract

A polyhydroxyalkanoate (PHA) copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)], was biosynthesized from biphenyl as the sole carbon source using Alcaligenes (currently Achromobacter) denitrificans A41. This strain is capable of degrading polychlorinated biphenyls (PCBs) and biphenyl. This proof-of-concept of the conversion of aromatic chemicals such as the environmental pollutant PCBs/biphenyl to eco-friendly products such as biodegradable polyester PHA was inspired by the uncovering of two genes encoding PHA synthases in the A. denitrificans A41 genome. When the carbon/nitrogen (C/N) ratio was set at 21, the cellular P(3HB-co-3HV) content in strain A41 reached its highest value of 10.1% of the cell dry weight (CDW). A two-step cultivation protocol improved the accumulation of P(3HB-co-3HV) by up to 26.2% of the CDW, consisting of 13.0 mol % 3HV when grown on minimum salt medium without nitrogen sources. The highest cellular content of P(3HB-co-3HV) (47.6% of the CDW) was obtained through the two-step cultivation of strain A41 on biphenyl as the sole carbon source. The purified copolymer had ultra-high molecular weight (weight-average molecular weight of 3.5 × 10 6), as revealed through gel-permeation chromatography. Based on the genomic information related to both polymer synthesis and biphenyl degradation, we finally proposed a metabolic pathway for the production of P(3HB-co-3HV) associated with the degradation of biphenyl by strain A41.

Producción de plásticos biodegradables a partir de bacterias de hábitats salinos aisladas de la Laguna de Ayarza

“…Por otra parte, durante este estudio también se encontraron cinco cepas de A. fecalis capaces de producir PHA (identificadas con los códigos AP21-01, AP21-10, AP21-14, AP21-26 y AP21-30) las cuales evidenciaron los mayores valores medios de producción por litro de sustrato. Diversas especies de Alcaligenes han sido reportadas por otros autores como productoras de PHA principalmente poli(3-hidroxibutirato) (PHB) y poli (3-hidroxibutiratoco-3-hidroxivalerato) (PHBV); se ha reportado que su diversidad metabólica, capacidad de utilizar compuestos aromáticos y metales pesados, así como su capacidad para eliminar productos tóxicos, ha vuelto de interés a este género para la producción de PHA (Yajima et al, 2020).…”

From Organic Wastes and Hydrocarbons Pollutants to Polyhydroxyalkanoates: Bioconversion by Terrestrial and Marine Bacteria

“…Alcaligenes denitrificans A41 was cultivated in the presence of biphenyl as the sole substrate, in two steps: the first aimed at obtaining biomass in the stationary growth phase; during the second phase, the medium was depleted of nitrogen and supplemented with biphenyl. The PHA content reached was up to 47.6% of the CDW [143].…”

Evaluation of polyhydroxyalkanoate (PHA) synthesis by Pichia sp. TSLS24 yeast isolated in Vietnam

“…In general, preference of C/N ratio varies with the type of strain, carbon, and nitrogen source. Different optimum C/N ratios were reported for PHA production in various microbes, such as 40:1 for Pseudomonas mendocina 45 , 21:1 for Alcaligenes denitrifcans A41 46 , and 15:1 for Bacillus megaterium 47 . C/N ratio of 20:1 was also reported to be optimum for the accumulation of poly-3-hydroxybutyrate-co-3-hydroxyhexanoate up to 67 wt% in Ralstonia eutropha using coffee waste oil as carbon source and ammonium chloride as nitrogen source 48 .…”