Food waste conversion to microbial polyhydroxyalkanoates.

Chad Nielsen,Charles D Miller,Marie K Walsh,Asad Ur Rehman,Asif Rahman

doi:10.1111/1751-7915.12776

Chad Nielsen, Charles D Miller + Show 3 more

Open Access

https://doi.org/10.1111/1751-7915.12776

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Abstract

SummaryPolyhydroxyalkanoates (PHAs) are biopolymers with desirable material properties similar to petrochemically derived plastics. PHAs are naturally produced by a wide range of microorganisms as a carbon storage mechanism and can accumulate to significantly high levels. PHAs are an environmentally friendly alternative to their petroleum counterparts because they can be easily degraded, potentially reducing the burden on municipal waste systems. Nevertheless, widespread use of PHAs is not currently realistic due to a variety of factors. One of the major constraints of large‐scale PHA production is the cost of carbon substrate for PHA‐producing microbes. The cost of production could potentially be reduced with the use of waste carbon from food‐related processes. Food wastage is a global issue and therefore harbours immense potential to create valuable bioproducts. This article's main focus is to examine the state of the art of converting food‐derived waste into carbon substrates for microbial metabolism and subsequent conversion into PHAs.

Highlights

Produced polyhydroxyalkanoates (PHAs) are among the most well-studied biologically derived plastics
There are over 155 confirmed unique PHA monomer subunits, which demonstrates the diversity of potential PHA polymers that can be produced using microorganisms (Agnew and Pfleger, 2013)
Cupriavidus necator has been recorded to have as high as 74% of its cell weight as PHB and recombinant Escherichia coli have been recorded to accumulate up to 85% of their dry cell weight as PHB (Kim et al, 1994; Wang et al, 2009)

Summary

Introduction

Produced polyhydroxyalkanoates (PHAs) are among the most well-studied biologically derived plastics. Apart from C. necator mRePT, these organisms are capable of utilizing whey to produce PHAs with more desirable properties than PHB Starch is another carbon source derived from food wastes that has been studied for production of PHAs. Starch is a glucose polymer produced by plants such as rice, wheat, potatoes, maize and cassava. 54 g lÀ1 dry cell weight with 46% PHB was obtained with oxygen limitation (Table 1) These studies indicate that high concentrations of cells containing PHAs are possible on starchy food wastes, even with minimal pre-treatments in the case of the Kim (2000) study. Another notable finding is that when tallow was used as a carbon source, the copolymer PHBV was produced instead of pure PHB (Table 1)

Conclusions and outlook

Findings

Conflict of interest