Prospects for the Use of Whey for Polyhydroxyalkanoate (PHA) Production

Abstract

Plastic production and accumulation have devastating environmental effects, and consequently, the world is in need of environmentally friendly plastic substitutes. In this context, polyhydroxyalkanoates (PHAs) appear to be true alternatives to common plastics because they are biodegradable and biocompatible and can be biologically produced. Despite having comparable characteristics to common plastics, extensive PHA use is still hampered by its high production cost. PHAs are bacterial produced, and one of the major costs associated with their production derives from the carbon source used for bacterial fermentation. Thus, several industrial waste streams have been studied as candidate carbon sources for bacterial PHA production, including whey, an environmental contaminant by-product from the dairy industry. The use of whey for PHA production could transform PHA production into a less costly and more environmentally friendly process. However, the efficient use of whey as a carbon source for PHA production is still hindered by numerous issues, including whey pre-treatments and PHA producing strain choice. In this review, current knowledge on using whey for PHA production were summarized and new ways to overcome the challenges associated with this production process were proposed.

Keywords: PHA; PHB; bioplastics; environment; lactose; polyhydroxyalkanoate; whey.

FIGURE 1

Schematic diagram of possible pathways for the production of polyhydroxyalkanoates from whey. Whole whey can be directly used in fermentations that produce PHAs. However, pre-treatments are normally used to generate efficient PHA production. Production of ricotta cheese from whey generates a by-product called ricotta cheese whey or scotta. Scotta can be used directly or after undergoing pre-treatments for PHA production. PHA production from whey can be achieved by using organisms that occur in nature and are capable of producing PHAs from whey or whey derivatives (wild-type strains); engineered strains enhanced for PHA production or lactose consumption (engineered strains); or mixed microbial cultures (MMCs) that can originate from waste streams or nature and can be enriched in PHA producing microorganisms usually using feast and famine cycles. During PHA production, waste streams are generated that can be used as additives for new fermentations from whey or scotta.