Search for Inexpensive Carbon Substrates

Economic evaluation of the bacterial process for poly(3HB) production suggests that the cost of the carbon substrate accounts for up to 50 % of the total cost of poly(3HB) production (Choi and Lee 1997). A successful bacterial process for PHA production hence depends on the availability of a low-cost carbon substrate. Besides carbohydrates, organic acids and short-chain alcohols are also potential carbon substrates for the industrial production of PHAs. The cellular toxicity of the latter compounds, however, requires the isolation or identification of PHA producers that are more tolerant to these compounds. Reported progress includes the production of PHAs from whey or acetic and butyric acids. 

Whey is a major by-product in the manufacturing of cheese or casein from milk. Whey from bovine milk contains approximately 4.5 % (wt/vol) lactose, 0.8 % (wt/vol) protein, 0.1-0.8 % (wt/vol) lactic acid, and 1 % (wt/vol) salts (Wong and Lee 1998). 

Organic Add and Solvent Production Acetic, Lactic, Gluconic, Succinic, and Polyhydroxyalkanoic Acids 

In the United States, only half of the whey is recycled into useful products such as food ingredients and animal feed (Ahn et al. 

In localities where the disposal of whey is a problem, the production of PHA from this carbon source should provide a higher economical return. 

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