Integrated systems for biopolymers and bioenergy production from organic waste and by-products: a review of microbial processes

Abstract

Recently, issues concerning the sustainable and harmless disposal of organic solid waste have generated interest in microbial biotechnologies aimed at converting waste materials into bioenergy and biomaterials, thus contributing to a reduction in economic dependence on fossil fuels. To valorize biomass, waste materials derived from agriculture, food processing factories, and municipal organic waste can be used to produce biopolymers, such as biohydrogen and biogas, through different microbial processes. In fact, different bacterial strains can synthesize biopolymers to convert waste materials into valuable intracellular (e.g., polyhydroxyalkanoates) and extracellular (e.g., exopolysaccharides) bioproducts, which are useful for biochemical production. In particular, large numbers of bacteria, including Alcaligenes eutrophus, Alcaligenes latus, Azotobacter vinelandii, Azotobacter chroococcum, Azotobacter beijerincki, methylotrophs, Pseudomonas spp., Bacillus spp., Rhizobium spp., Nocardia spp., and recombinant Escherichia coli, have been successfully used to produce polyhydroxyalkanoates on an industrial scale from different types of organic by-products. Therefore, the development of high-performance microbial strains and the use of by-products and waste as substrates could reasonably make the production costs of biodegradable polymers comparable to those required by petrochemical-derived plastics and promote their use. Many studies have reported use of the same organic substrates as alternative energy sources to produce biogas and biohydrogen through anaerobic digestion as well as dark and photofermentation processes under anaerobic conditions. Therefore, concurrently obtaining bioenergy and biopolymers at a reasonable cost through an integrated system is becoming feasible using by-products and waste as organic carbon sources. An overview of the suitable substrates and microbial strains used in low-cost polyhydroxyalkanoates for biohydrogen and biogas production is given. The possibility of creating a unique integrated system is discussed because it represents a new approach for simultaneously producing energy and biopolymers for the plastic industry using by-products and waste as organic carbon sources.

Evaluation of organic fractions of municipal solid waste as renewable feedstock for succinic acid production

“…The carbohydrate content of OFMSW is 30-60% depending on the origin of the waste and the region among other factors. The OFMSW has been evaluated for the production of polyhydroxyalkanoates (PHAs), biogas and biohydrogen via mixed cultures [4][5][6] as well as the production of bio-based fuels and platform chemicals, such as bioethanol, lactic acid and succinic acid, via single strain fermentations [7][8][9].…”

Scale‐up and Sustainability Evaluation of Biopolymer Production from Citrus Waste Offering Carbon Capture and Utilisation Pathway

“…Third, the separation sequences should be rigorously optimised to reduce the heating duties in distillation columns. Finally, it is important to recognise that the biowaste feedstock could be used as an energy source as well as a raw material for the process …”

Hydrogen‐Driven Cofactor Regeneration for Stereoselective Whole‐Cell C=C Bond Reduction in Cupriavidus necator

“…ee values recorded for biotransformations of 3a under fructosedriven (black squares) and hydrogen-driven (red circles)c onditions. C. necator is already being intenselys tudied and tested for the productiono fb iopolymers and bioenergy from al arge variety of organic wastestreams; [19,20] therefore, the infrastructure foru pscaling is predicted to be available in the foreseeable future.A lthough a purely hydrogen-driven autotrophic system would be advantageous, it remains possible to grow cells in diauxic batch cultures to allow the expression of the soluble hydrogenase under heterotrophic conditions. This is not the case for its fructose-driven counterpart, which decreases consistently across 48 ho freaction time, indicating product racemization (n = 3).…”

“…[18] We envisage that the wide-spread application of hydrogendriven biotransformations can play ap otentially large role in the future of biocatalytic reactions. C. necator is already being intenselys tudied and tested for the productiono fb iopolymers and bioenergy from al arge variety of organic wastestreams; [19,20] therefore, the infrastructure foru pscaling is predicted to be available in the foreseeable future.A lthough a purely hydrogen-driven autotrophic system would be advantageous, it remains possible to grow cells in diauxic batch cultures to allow the expression of the soluble hydrogenase under heterotrophic conditions. [21] This approachm ay potentially allow for high biomass accumulation and simultaneous exploitation of C. necator's ability to thrive mixotrophically.…”