ABSTRACT
Large-scale production of polyhydroxyalkanoates (PHA) is mainly limited by the high cost of the raw materials used as substrates. However, huge amounts of inexpensive residues, such as whey, molasses, waste glycerol and lipids, and starchy and lignocellulosic substrates, are available and could be potentially used for industrial PHA production. Unfortunately, wild-type strains for the direct and efficient conversion of low-cost waste streams into PHA are not available in nature, and therefore the engineering of strains became the key factor.
There are two possible approaches: (i) the engineering of highly efficient PHA producing microorganisms for their use of waste streams, or (ii) the engineering of bacteria naturally able to use complex and inexpensive carbon sources, but unable to produce PHA.
This chapter summarizes the recent relevant results dealing with PHA production from a large selection of organic byproducts by means of engineered microbes developed using the two above-mentioned approaches. The most relevant and recent genomic tools for the genetic modification are initially described, with emphasis on hosts, genes, plasmids, promoters, and gene copy number.
