Production of polyhydroxyalkanoates using a novel, metagenomics identified, class III synthase

Polyhydroxyalkanoates are a microbial storage polymer that presents similar characteristics to plastics, therefore are usually referred to as bioplastics . The key enzyme involved in the synthesis of polyhydroxyalkanoates is called PHA synthase, but it is always forming a synthesis cassette of three to five enzymes.In this work, we present a novel class III polyhydroxyalkanoate synthesis cluster identified using a sequence-based metagenomics approach. From two metagenomes from dairy industries stabilization ponds, we found four complete synthesis cassettes. One of them was successfully cloned into Escherichia coli GCSC 6576, a bacterial strain able to grow in lactose and whey permeate, a by-product of dairy industries that represent an environmental risk.This recombinant strain grown in lactose was able to produce acumulate nearly 40% of dry weight as insolubre material characterized by GC-FID as poly(3-hydroxybutyrate) one of the main polyhydroxyalkanoates commercially used.This research presents the complete process, from the identification of novel enzymes from uncultured microorganisms to the synthesis at laboratory scale of compounds of industrial interest.