Advances in Polyhydroxyalkanoate (PHA) Production, Volume 2 (original) (raw)
Related papers
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....
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.
Recent developments in bioreactor scale production of bacterial polyhydroxyalkanoates
Bioprocess and Biosystems Engineering, 2019
Polyhydroxyalkanoates (PHAs) are biological plastics that are sustainable alternative to synthetic ones. Numerous microorganisms have been identified as PHAs producers they store PHAs as cellular inclusions to use as an energy source backup. They can be produced in shake flasks and in bioreactors under defined fermentation and physiological culture conditions using suitable nutrients. Their production at bioreactor scale depends on various factors such as carbon source, nutrients supply, temperature, dissolved oxygen level, pH and processes. Once produced, PHAs find diverse applications in multiple fields of science and technology particularly in the medical sector. The present review covers some recent developments in sustainable bioreactor scale production of PHAs and identifies some areas in which future research in this field might be focused.
Potential and Prospects of Continuous Polyhydroxyalkanoate (PHA) Production
Bioengineering, 2015
Together with other so-called "bio-plastics", Polyhydroxyalkanoates (PHAs) are expected to soon replace established polymers on the plastic market. As a prerequisite, optimized process design is needed to make PHAs attractive in terms of costs and quality. Nowadays, large-scale PHA production relies on discontinuous fed-batch cultivation in huge bioreactors. Such processes presuppose numerous shortcomings such as nonproductive time for reactor revamping, irregular product quality, limited possibility for supply of certain carbon substrates, and, most of all, insufficient productivity. Therefore, single-and multistage continuous PHA biosynthesis is increasingly investigated for production of different types of microbial PHAs; this goes for rather crystalline, thermoplastic PHA homopolyesters as well as for highly flexible PHA copolyesters, and even blocky-structured PHAs consisting of alternating soft and hard segments. Apart from enhanced productivity and constant product quality, chemostat processes can be used to elucidate kinetics of cell growth and PHA formation under constant process conditions. Furthermore, continuous enrichment processes constitute a tool to isolate novel powerful PHA-producing microbial strains adapted to special environmental conditions. The article discusses challenges, potential and case studies for continuous PHA production, and shows up new strategies to further enhance such processes economically by developing unsterile open continuous processes combined with the application of inexpensive carbon feedstocks.
Review Potential and Prospects of Continuous Polyhydroxyalkanoate (PHA) Production
2016
Together with other so-called "bio-plastics", Polyhydroxyalkanoates (PHAs) are expected to soon replace established polymers on the plastic market. As a prerequisite, optimized process design is needed to make PHAs attractive in terms of costs and quality. Nowadays, large-scale PHA production relies on discontinuous fed-batch cultivation in huge bioreactors. Such processes presuppose numerous shortcomings such as nonproductive time for reactor revamping, irregular product quality, limited possibility for supply of certain carbon substrates, and, most of all, insufficient productivity. Therefore, single-and multistage continuous PHA biosynthesis is increasingly investigated for production of different types of microbial PHAs; this goes for rather crystalline, thermoplastic PHA homopolyesters as well as for highly flexible PHA copolyesters, and even blocky-structured PHAs consisting of alternating soft and hard segments. Apart from enhanced productivity and constant product quality, chemostat processes can be used to elucidate kinetics of cell growth and PHA formation under constant process conditions. Furthermore, continuous enrichment processes constitute a tool to isolate novel powerful PHA-producing microbial strains adapted to special environmental conditions. The article discusses challenges, potential and case studies for continuous PHA production, and shows up new strategies to further enhance such processes economically by developing unsterile open continuous processes combined with the application of inexpensive carbon feedstocks.
Recent advances in polyhydroxyalkanoate production by bacterial fermentation: mini-review
International Journal of Biological Macromolecules, 1999
Poly(3-hydroxybutyrate) [P(3HB)] and other polyhydroxyalkanoates (PHAs) have been drawing much attention as biodegradable substitutes for conventional nondegradable plastics. For the economical production of P(3HB), various bacterial strains, either wild-type or recombinant, and new fermentation strategies were developed for the production of P(3HB) with high concentration and productivity. To reduce the cost of carbon substrate, several processes for P(3HB) production from cheap carbon sources were also developed. P(3HB) can now be produced to a content of 80% of cell dry weight with the productivity greater than 4 g/l per h. Fermentation strategy was also developed for the efficient production of medium chain length PHA by high cell density culture. With all these advances, P(3HB) and PHAs can be produced by bacterial fermentation at a cost (ca. $2/kg) similar to that of other biodegradable polymers under development.
Biotechnological Production of Polyhydroxyalkanoates: A Review on Trends and Latest Developments
Chinese Journal of Biology, 2014
Polyhydroxyalkanoates (PHA) producers have been reported to reside at various ecological niches which are naturally or accidently exposed to high organic matter or growth limited conditions such as dairy wastes, hydrocarbon contaminated sites, pulp and paper mill wastes, agricultural wastes, activated sludges of treatment plants, rhizosphere, and industrial effluents. Few among them also produce extracellular by-products like rhamnolipids, extracellular polymeric substances, and biohydrogen gas. These sorts of microbes are industrially important candidates for the reason that they can use waste materials of different origin as substrate with simultaneous production of valuable bioproducts including PHA. Implementation of integrated system to separate their by-products (intracellular and extracellular) can be economical in regard to production. In this review, we have discussed various microorganisms dwelling at different environmental conditions which stimulate them to accumulate ca...
Many bacterial species, such as the chemolytotrophs Cupriavidus necator (Ralstonia eutropha), Cupriavidus metallidurans and Alcaligenes latus [4], Pseudomonas putida, P. aeruginosa , P. pseudoflava and other Pseudomonas spp [16], Azotobacter vinelandii [17], Halomonas campisalis [18], Enterobacter spp. [19], Thermus thermophilus [20]; Bacillus subtilis [21,22] and Bacillus cereus [23] among others, can synthesise and accumulate and store polyhydroxyalkanoates (PHAs) in intracellular organelles [24], co-polymers composed of hydroxypropionate, hydroxybutyrate and hydroxyvalerate, depending on the availability of precursors (such as octanoic acid) [11,25-27] and intermediate compounds regulating the
Polymers
In the growing polymer industry, the interest of researchers is captivated by bioplastics production with biodegradable and biocompatible properties. This study examines the polyhydroxyalkanoates (PHA) production performance of individual Lysinibacillus sp. RGS and Ralstonia eutropha ATCC 17699 and their co-culture by utilizing sugarcane bagasse (SCB) hydrolysates. Initially, acidic (H2SO4) and acidified sodium chlorite pretreatment was employed for the hydrolysis of SCB. The effects of chemical pretreatment on the SCB biomass assembly and its chemical constituents were studied by employing numerous analytical methods. Acidic pretreatment under optimal conditions showed effective delignification (60%) of the SCB biomass, leading to a maximum hydrolysis yield of 74.9 ± 1.65% and a saccharification yield of 569.0 ± 5.65 mg/g of SCB after enzymatic hydrolysis. The resulting SCB enzymatic hydrolysates were harnessed for PHA synthesis using individual microbial culture and their defined ...