Recovery of polyhydroxyalkanoates (PHAs) from wastewater: A review (original) (raw)
Related papers
Producing microbial polyhydroxyalkanoate (PHA) biopolyesters in a sustainable manner
A B S T R A C T Sustainable production of microbial polyhydroxyalkanoate (PHA) biopolyesters on a larger scale has to consider the " four magic e " : economic, ethical, environmental, and engineering aspects. Moreover, sustainability of PHA production can be quantified by modern tools of Life Cycle Assessment. Economic issues are to a large extent affected by the applied production mode, downstream processing, and, most of all, by the selection of carbon-rich raw materials as feedstocks for PHA production by safe and naturally occurring wild type microorganisms. In order to comply with ethics, such raw materials should be used which do not interfere with human nutrition and animal feed supply chains, and shall be convertible towards accessible carbon feedstocks by simple methods of upstream processing. Examples were identified in carbon-rich waste materials from various industrial braches closely connected to food production. Therefore, the article shines a light on hetero-, mixo-, and autotrophic PHA production based on various industrial residues from different branches. Emphasis is devoted to the integration of PHA-production based on selected raw materials into the holistic patterns of sustainability; this encompasses the choice of new, powerful microbial production strains, non-hazardous, environmentally benign methods for PHA recovery, and reutilization of waste streams from the PHA production process itself.
Waste to bioplastics: How close are we to sustainable polyhydroxyalkanoates production?
Waste Management, 2021
Increased awareness of environmental sustainability with associated strict environmental regulations has incentivized the pursuit of novel materials to replace conventional petroleum-derived plastics. Polyhydroxyalkanoates (PHAs) are appealing intracellular biopolymers and have drawn significant attention as a viable alternative to petrochemical based plastics not only due to their comparable physiochemical properties but also, their outstanding characteristics such as biodegradability and biocompatibility. This review provides a comprehensive overview of the recent developments on the involved PHA producer microorganisms, production process from different waste streams by both pure and mixed microbial cultures (MMCs). Bio-based PHA production, particularly using cheap carbon sources with MMCs, is getting more attention. The main bottlenecks are the low production yield and the inconsistency of the biopolymers. Bioaugmentation and metabolic engineering together with cost effective downstream processing are promising approaches to overcome the hurdles of commercial PHA production from waste streams.
Production of Polyhydroxyalkanoates from Renewable Sources Using Bacteria
Journal of Polymers and the Environment, 2018
Plastics play a very important role in our daily life. They are used for various purposes. But the disposal of these petrochemical-derived plastics causes a risk to the human and marine population, wildlife and environment. Also, due to the eventual depletion of petrochemical sources, there is a need for the development of alternate sources for the production of plastics. Biodegradable polymers produced by microorganisms can be used as substitutes for conventional plastics derived from petrochemical sources since they have similarity in their properties. Polyhydroxyalkanoate (PHA) is one such biopolymer that will be accumulated inside the cells of microorganisms as granules for energy storage under limiting conditions of nutrients and high concentration of carbon. Research on the microbial production of PHA should focus on the identification of costeffective substrates and also identification of a suitable strain of organism for production. The major focus of this review is the production of PHA from various cost-effective substrates using different bacterial species. The review also covers the biosynthetic pathway of PHA, extraction method, characterization technique, and applications of PHA in various sectors.
The EuroBiotech Journal, 2020
Downstream processing for recovery of microbial polyhydroxyalkanoate (PHA) biopolyesters from biomass constitutes an integral part of the entire PHA production chain; beside the feedstocks used for cultivation of PHA-production strains, this process is currently considered the major cost factor for PHA production. Besides economic aspects, PHA recovery techniques need to be sustainable by avoiding excessive use of (often precarious!) solvents, other hazardous chemicals, non-recyclable compounds, and energy. Moreover, the applied PHA recovery method is decisive for the molecular mass and purity of the obtained product, and the achievable recovery yield. In addition to the applied method, also the PHA content in biomass is decisive for the feasibility of a selected technique. Further, not all investigated recovery techniques are applicable for all types of PHA (crystalline versus amorphous PHA) and all PHA-producing microorganisms (robust versus fragile cell structures). The present r...
2018
Polyhydroxyalkanoates (PHA) are microbial biopolyesters utilized as “green plastics”. Their production under controlled conditions resorts to bioreactors operated in different modes. Because PHA biosynthesis constitutes a multiphase process, both feeding strategy and bioreactor operation mode need smart adaptation. Traditional PHA production setups based on batch, repeated batch, fed-batch or cyclic fed-batch processes are often limited in productivity, or display insufficient controllability of polyester composition. For highly diluted substrate streams like it is the case for (agro)industrial waste streams, fed-batch enhanced by cell recycling were recently reported as a viable tool to increase volumetric productivity. As emerging trend, continuous fermentation processes in single-, two-, and multi-stage setups are reported, which bring the kinetics of both microbial growth and PHA accumulation into agreement with process engineering, and allow tailoring PHA´s molecular structure....
Bacterially Produced Polyhydroxyalkanoate (PHA): Converting Renewable Resources into Bioplastics
Dependence on conventional plastics and their boundless usage have resulted in waste accumulation and greenhouse gas emissions. Recent technologies are directed towards the development of bio-green materials that exert negligible sideeffects on the environment. A biologically-synthesized plastic, polyhydroxyalkanoate (PHA), has been attracting major interests due to its similar physical properties to synthetic plastics. Unlike synthetic plastics, PHA is produced from renewable resources and is degraded aerobically by microorganisms to CO 2 and H 2 O upon disposal. The selections of suitable bacterial strains, inexpensive carbon sources, efficient fermentation and recovery processes are important aspects that should be taken into consideration for the commercialization of PHA. This chapter discusses economical strategies to reduce production costs of PHA as well as its applications in various fields.
Highly efficient separation and purification of polyhydroxyalkanoates (PHAs) from PHA-containing cell mass is essential for the production of bioplastics from renewable resources in a cost-effective, environmentally friendly way. Combination of digestion and selective dissolution of non-PHA cell mass (NPCM) using low concentration of sodium hypochlorite of PHA biopolymers, a simple process is developed and has demonstrated to recover PHA from cell mass to high purity (>90 wt %) with high yield (>90 wt %). Saponification was applied to separate or remove oil from the PHA-particles. This method was adopted in this study and was able to increase the PHA extraction from the mixed microbial intracellular biomass up to 85% of cell dried weight (CDW).
Bioresource Technology, 2012
Production of biodegradable plastics in the form of polyhydroxyalkanoates (PHA) especially from renewable substrates is gaining interest. The present work mainly aims to investigate the influence of substrate load and nutrient concentration (nitrogen and phosphorous) on PHA production using wastewater as substrate and mixed culture as biocatalyst. PHA accumulation was high at higher substrate load [OLR3, 40.3% of dry cell weight (DCW)], low nitrogen (N 1 , 45.1% DCW) and low phosphorous (P 1 , 54.2% DCW) conditions. With optimized nutrient conditions production efficiency increased by 14%. Fractional composition of PHA showed co-polymer [poly(b-OH) butyrate-co-poly(b-OH) valerate, P3(HB-co-HV)] contains PHB (88%) in more concentration compared to PHV (8%). Dehydrogenase and phosphatase enzymatic activities were monitored during process operation. Good substrate degradation (as COD) of 75% was registered during PHA production. The phylogenetic profile of 16S rRNA sequencing showed the dominance of Firmicutes (71.4%) and Proteobacteria (28.6%), which are known to involve in PHA accumulation and waste treatment.
2022
Diminishing sources of synthetic plastics and their unsustainable production processes have increased the demand for alternative biodegradable and sustainable polymers. Bacterial biopolymer-producing factories can carry out large-scale production of such alternatives using improved fermentation techniques, such as fed-batch and pulsed feeding of inducers, that can increase bacterial biopolymer accumulation. However, the successive downstream processing (DSP) techniques still pose challenges in making the production process both economically and environmentally sustainable. These challenges are mostly associated with biomass pre-treatment, the use of solvents, and the embedded parameters of the DSP techniques. Conventional halogenated/chlorinated solvents can be substituted with green solvents to yield PHAs of high purity (98%) for high-end applications and to establish a sustainable circular economy. As an economically and environmentally sustainable approach, the use of recycled waste as a substrate and greener extraction solvents for bacterial biopolymer production should be further explored for the efficient replacement of synthetic plastic production.