Robust microorganisms for biofuel and chemical production from municipal solid waste

Abstract

Background: Worldwide 3.4 billion tonnes of municipal solid waste (MSW) will be produced annually by 2050, however, current approaches to MSW management predominantly involve unsustainable practices like landfilling and incineration. The organic fraction of MSW (OMSW) typically comprises ~ 50% lignocellulose-rich material but is underexplored as a biomanufacturing feedstock due to its highly inconsistent and heterogeneous composition. This study sought to overcome the limitations associated with studying MSW-derived feedstocks by using OMSW produced from a realistic and reproducible MSW mixture on a commercial autoclave system. The resulting OMSW fibre was enzymatically hydrolysed and used to screen diverse microorganisms of biotechnological interest to identify robust species capable of fermenting this complex feedstock. Results:The autoclave pre-treated OMSW fibre contained a polysaccharide fraction comprising 38% cellulose and 4% hemicellulose. Enzymatic hydrolysate of OMSW fibre was high in d-glucose (5.5% w/v) and d-xylose (1.8%w/v) but deficient in nitrogen and phosphate. Although relatively low levels of levulinic acid (30 mM) and vanillin (2 mM) were detected and furfural and 5-hydroxymethylfurfural were absent, the hydrolysate contained an abundance of potentially toxic metals (0.6% w/v). Hydrolysate supplemented with 1% yeast extract to alleviate nutrient limitation was used in a substrate-oriented shake-flask screen with eight biotechnologically useful microorganisms (Clostridium saccharoperbutylacetonicum, Escherichia coli, Geobacillus thermoglucosidasius, Pseudomonas putida, Rhodococcus opacus, Saccharomyces cerevisiae, Schizosaccharomyces pombe and Zymomonas mobilis). Each species' growth and productivity were characterised and three species were identified that robustly and efficiently fermented OMSW fibre hydrolysate without significant substrate inhibition: Z. mobilis, S. cerevisiae and R. opacus, respectively produced product to 69%, 70% and 72% of the maximum theoretical fermentation yield and could theoretically produce 136 kg and 139 kg of ethanol and 91 kg of triacylglycerol (TAG) per tonne of OMSW. Conclusions: Developing an integrated biorefinery around MSW has the potential to significantly alleviate the environmental burden of current waste management practices. Substrate-oriented screening of a representative and reproducible OMSW-derived fibre identified microorganisms intrinsically suited to growth on OMSW hydrolysates. These species are promising candidates for developing an MSW biorefining platform and provide a foundation for future studies aiming to valorise this underexplored feedstock. © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third part...

Rhodococcus as Biofactories for Microbial Oil Production

“…Dornau et al analyzed the potential of eight biotechnologically useful microorganisms ( Clostridium saccharoperbutylacetonicum , Escherichia coli , Geobacillus thermoglucosidasius , Pseudomonas putida , Rhodococcus opacus , Saccharomyces cerevisiae , Schizosaccharomyces pombe , and Zymomonas mobilis ) to grow and produce diverse bioproducts from OMSW. Enzymatic hydrolysate of OMSW fiber contained high concentrations of glucose (5.5%, w / v ) and xylose (1.8%, w / v ) but was deficient in nitrogen and phosphate [ 91 ]. Interestingly, three species ( Z. mobilis , S. cerevisiae, and R. opacus ) became more efficient during OMSW fiber hydrolysate fermentation.…”

“…Interestingly, three species ( Z. mobilis , S. cerevisiae, and R. opacus ) became more efficient during OMSW fiber hydrolysate fermentation. R. opacus MITXM-61 produced TAG to 72% of the maximum theoretical fermentation yield and could theoretically produce 91 kg of TAG per tonne of OMSW [ 91 ]. R. opacus MITXM-61 is an engineered strain [ 95 ] with the ability to simultaneously utilize D-glucose and D-xylose in lignocellulosic hydrolysates.…”

“…The TAG produced by R. opacus grown on OMSW fiber exhibited the typical fatty acid composition of this species, including C 14 –C 18 fatty acyl-residues with an abundance of palmitic acid. This study demonstrated that R. opacus is well-suited for growth and lipid production on OMSW fiber hydrolysate and that this residual material is another potential feedstock for producing biofuels and chemicals [ 91 ].…”

Enzyme digestion of biofiber from mechanical heat treated municipal solid waste: Accessing kinetic and rheological design data using a pilot-scale high-solids mixer

“…Typically, the moisture content of the as-made biofiber was around 70% on total wet weight. Previous analyses had shown that the biofiber from the standardized MSW comprised of approximately 58% w/w lignocellulose, of which 65.5% was cellulose (38% of total fibre), 27.6% was lignin (16% of total fibre) and 6.9% was hemicellulose (4% of total fibre) [18]. The high cellulose content suggested that the biofiber would be a practicable fermentation feedstock.…”

Bacterial Diversity and Community Structure of a Municipal Solid Waste Landfill: A Source of Lignocellulolytic Potential

“…Much research states that microorganisms are still the biggest group of undescribed biodiversity and that they are a bewildering source of exploitable diversity [1]. Municipal solid waste (MSW) refers to waste coming out of homes and institutions, and over 2 billion tonnes are produced worldwide on an annual basis, with a 2050 projection of 3.4 billion tonnes [2]. The collection, management, and disposal of MSW are a huge environmental issue causing huge environmental problems such as air, water, soil, and esthetic pollution [3].…”