In Silico Reconstitution of Novel Routes for Microbial Plastic

Abstract

Polyhydroxyalkanoate (PHA) biosynthesis is a phenotype expressed under environmental stress. PHA synthesis relies on important intermediates tricarboxylic acid (TCA) cycle and fatty acid metabolism especially acetyl CoA. Acetyl CoA is in demand by a host of metabolisms and is not easily available under normal “unstressed” conditions. This work was done to find out alternative routes for copolymer polyhydroxybutyrate (PHB), which may exist in nature but not explored so far. Using metabolic pathway database (KEGG), we have devised in silico novel metabolic pathways, which are independent of acetyl CoA, i.e., may operate under different conditions. Moreover, organisms possessing enzymes for these simulated PHB production routes have also been identified. In this comparative analysis, we found some potential organisms such as Brucella, Deinococcus, Homo sapiens, Mus musculus, Rattus, Thermoanaerobacter, and Xanthomonas which have the necessary genetic machinery for one or more of these novel pathways. Incidentally, they have not been reported previously as PHB producers. On the other hand, these novel routes have also been observed in certain known PHB producers such as Clostridium, Ralstonia, Pseudomonas, and Mesorhizobium. The advantage of these novel routes in known PHB producers is expanding the source of starting material for PHB synthesis.