Pilot scale polyhydroxyalkanoates-production from organic fraction of municipal solid waste by Hydrogenophaga species

Plastic pollution represents a worldwide threat to environment, nevertheless during last decades promising alternatives to conventional plastics have been investigated. The use of biodegradable polymers produced by microorganisms, such as polyhydroxyalkanoates (PHA), are of high interest due to their thermo-plastic properties. Recently, the PHA-production from the Organic Fraction of Municipal Solid Waste (OFMSW) was successfully reported at pilot scale. In particular, this work is aimed at evaluating the microbial community dynamics during plant operation (around 200 days) and correlating the occurrence of specific PHA accumulating bacteria to process parameters (e.g. temperature, Volatile Fatty Acids composition, PHA content, Organic Loading Rate). Temporal changes in microbial community composition were described by high-throughput 16S rRNA gene sequencing and the outputs of the analysis were validated by applying specific FISH oligonucleotide probes. The Nile blue staining, specific for the detection of intracellular lipid inclusions, confirmed that the whole biomass was able to store PHA granules. Members of Hydrogenophaga genus were main PHA accumulating bacteria and found associated to the maximum PHA storage capacity. This genus strongly increased overtime together with the appearance of functional gene (phaC) coding for PHA synthase.