Microbial prospection of an Amazonian blackwater lake and whole-genome sequencing of bacteria capable of polyhydroxyalkanoate synthesis

Biopolymers are driving the plastic industry to the next generation of environmentally friendly bioproducts, considering green chemistry principles and contemporary economic concepts, such as environmental, social, and governance (ESG) criteria. Hence, microbial biopolymers arise in this context. Resulting from a natural carbon and energy storage process, polyhydroxyalkanoates are the raw material for a range of products based on plastic, with the advantage of being biodegradable in a short period of time. Discovering new biopolymers with different properties, carbon sources and PHA-related enzymes will facilitate market development as well as competition with petrochemical polymers. This work reports the experimental findings of PHA production and genomic data for two bacteria, Ralstonia pickettii and Aquitalea sp., isolated from a blackwater lake located in the ecological reserve of Tupe, Iranduba, AM, Brazil. They were able to produce PHB from carbon sources related to sugar, and R. pickettii also produced PHB from soybean oil and lignin derivatives. Whole-genome sequencing of these isolates enabled the identification of the genetic background to use other oxidizable carbon sources, such as lactic and malonic acids, amino acids, and lignin. Bacteria possibly capable of polyhydroxyalkanoate synthesis from lignin were investigated by genomics and chemistry of biomaterials. Aquitalea sp and Ralstonia pickettii isolated from a blackwater lake rich humic substances, showed great potential to be developed for this purpose. Canonical lignin degradation pathways, such as protocatechuate 4,5-dioxygenase-dependent pathway, CoA-dependent non-β-oxidation pathway of ferulic acid and β-ketoadipate pathway were mapped in their genomes. In addition, traces of P(3HB) were found when using vanillic and gallic acids as sole carbon source, which indicates that the downstream β-ketoadipate pathway is functional.