Biomediated production of structurally diverse poly(hydroxyalkanoates) from surplus streams of the animal processing industry

Abstract

For commercial success, enhanced poly(hydroxyalkanoate) (PHA) production must address both material performance and economic aspects. Conventional PHA production consumes expensive feedstocks dedicated to nutrition. Switching to carbon-rich (agro)industrial side-streams alleviates industrial disposal problems, preserves food resources, and can be economically superior. Processes developed in the recently performed EU-FP7 project ANIMPOL resort to lipid-rich surplus streams from slaughterhouses and the ren- dering industry; these materials undergo chemical transformation to crude glycerol phase (CGP) and bio- diesel. The saturated biodiesel share (SFAE) counteracts its applicability as a biofuel but, in addition to CGP, can be converted biotechnologically to PHAs. Depending on the applied microbial production strain and the selected carbon source (SFAE or CGP), thermoplastic short chain length PHA (scl-PHA), as well as elastome- ric to latex-like medium chain length PHA (mcl-PHA), can be produced from these inexpensive feed stocks. The article illustrates the biotechnological conversion of animal-based CGP and SFAE towards poly(3-hyd- roxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), respectively, by Cupriavi- dus necator strain DSM 545. SFAE conversion towards mcl-PHAs consisting of various saturated and unsatu- rated building blocks by two pseudomonades, Ps. citronellolis DSM 50332 and Ps. chlororaphis DSM 50083, are also shown. Together with the kinetics of the bioprocesses, the results from the characterization of isolated samples of these structurally diverse biopolyesters are compared; data demonstrate the high versatility of biopolymer properties making them applicable in various fields of the plastic market. In addition to the need for inexpensive carbon feed stocks, the article points to further hot spots of the PHA-production chain that must be considered in order to lower the overall PHA production costs, and to enhance product quality. The benefits arising from multistage continuous cultivation production set-ups, namely high-throughput pro- duction of PHA of predefined composition and constant quality, are especially discussed. Finally, contempo- rary approaches towards environmentally and ecologically sustainable PHA recovery from biomass are summarized.