Industrially useful microbial species for production of biofuels and chemicals from municipal solid waste

Abstract

Municipal solid waste (MSW) production is projected to reach 3.4 billion tonnes per annum by 2050. The majority of MSW produced globally is incinerated or diverted to landfill, both methods which pollute the environment and contribute substantially to climate change. The organic fraction of MSW (OMSW) typically comprises ∼50 % lignocellulosic material and presents an abundant renewable feedstock for producing biofuels and chemicals. An important step toward OMSW valorisation is the identification of suitable microorganisms capable of fermenting this highly inconsistent, heterogeneous and complex feedstock. We have characterised the fermentation performance of eight biotechnologically relevant microorganisms (Clostridium saccharoperbutylacetonicum, Escherichia coli, Geobacillus thermoglucosidasius, Pseudomonas putida, Rhodococcus opacus, Saccharomyces cerevisiae, Schizosaccharomyces pombe and Zymomonas mobilis) on enzymatic hydrolysate of OMSW fibre produced by a commercial autoclave pre-treatment. S. cerevisiaewas the most efficient ethanol producer, followed closely by Z. mobilis. Both species produced ethanol to high titre within 24 h, but neither could ferment xylose. The most effective performance was demonstrated by R. opacus, which consumed all available glucose and xylose concurrently over 72 h and produced a remarkably large yield of triacylglycerol (a biodiesel and aviation fuel precursor). This work demonstrates that OMSW is a promising renewable feedstock capable of supporting the growth several industrially useful microorganisms to high product titres. The best performing species identified here are interesting candidates to study further for application in a MSW biorefinery.