초록
<P><B>Abstract</B></P> <P>The potential of biogas (with and without H<SUB>2</SUB>S) and volatile fatty acids (VFAs) to support microbial growth and accumulation of polyhydroxyalkanoates (PHAs) in type II methanotrophs was evaluated batchwise under aerobic conditions. <I>Methylocystis hirsuta</I> was able to grow on artificial biogas (70% CH<SUB>4</SUB>, 29.5% CO<SUB>2</SUB>, 0.5% H<SUB>2</SUB>S) and accumulate PHA up to 45 ± 1% (wt.%) under N-limited conditions. The presence of CO<SUB>2</SUB> and H<SUB>2</SUB>S did not significantly influence the growth and PHA synthesis in <I>M. hirsuta</I> compared to control tests provided with pure CH<SUB>4</SUB> at similar concentrations. Likewise, the addition of VFAs to the cultivation broth at initial concentrations of 100–200 mg L<SUP>−1</SUP> did not hamper the growth of this strain on artificial biogas. Indeed, the addition of 10% extra carbon in the form of individual VFAs resulted in an increase in the maximum PHA yield and final PHA content up to 0.45–0.63 gPHA gSubstrate <SUP>1</SUP> and 48–54% (wt.%), respectively, at the expense of a higher energy demand. Valeric acid supplementation supported the highest 3-hydroxyvalerate content (13.5%) within the biocomposite. In this context, this study demonstrated for the first time that 3-hydroxyvalerate synthesis by <I>M. hirsuta</I> did not depend on CH<SUB>4</SUB> assimilation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biogas was a feasible feedstock for methanotrophic growth and PHA accumulation. </LI> <LI> VFAs concentrations of 100–200 mg L<SUP>−1</SUP> did not hamper methanotrophic growth. </LI> <LI> VFAs enhanced PHA yields and contents by 10–30%. </LI> <LI> 3-Hydroxyvalerate was synthesized under valeric acid cultivation with/without CH<SUB>4</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>