Substrate Concentration and Thermal Effects During Polyhydroxyalkanoate Bioproduction (original) (raw)
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Carbon Sources for Polyhydroxyalkanoates and an Integrated Biorefinery
International Journal of Molecular Sciences, 2016
Polyhydroxyalkanoates (PHAs) are a group of bioplastics that have a wide range of applications. Extensive progress has been made in our understanding of PHAs' biosynthesis, and currently, it is possible to engineer bacterial strains to produce PHAs with desired properties. The substrates for the fermentative production of PHAs are primarily derived from food-based carbon sources, raising concerns over the sustainability of their production in terms of their impact on food prices. This paper gives an overview of the current carbon sources used for PHA production and the methods used to transform these sources into fermentable forms. This allows us to identify the opportunities and restraints linked to future sustainable PHA production. Hemicellulose hydrolysates and crude glycerol are identified as two promising carbon sources for a sustainable production of PHAs. Hemicellulose hydrolysates and crude glycerol can be produced on a large scale during various second generation biofuels' production. An integration of PHA production within a modern biorefinery is therefore proposed to produce biofuels and bioplastics simultaneously. This will create the potential to offset the production cost of biofuels and reduce the overall production cost of PHAs.
Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyacids naturally synthesized in bacteria as a carbon reserves. Bacillus subtilis can synthesize and accumulate PHA as carbon source under limiting conditions of nutrients. PHAs are promising candidates for the development of environment-friendly, biodegradable plastics. The aim of the present work was to study the optimization of PHAs using different carbon sources in the media and by using agro-industrial bio-wastes as a replacement for the carbon source. The study also identifies the potential of the strain to produce maximum dry cell weight and PHA from the cheap sources, i.e. waste samples taken from different industries like distillery effluent, sugarcane molasses, milk whey, and paper industry effluent. The use of these low-cost raw materials has the potential to reduce PHA production costs, because the raw material cost contributes a significant part in traditional PHA production processes. On studying the effect of different carbon sources in the medium, it was found that sucrose-supplemented Luria-Bertani medium produced maximum PHA production of 1.58 mg/ml in 72 h constituting 58.59% w/w of the total cell dry mass at a pH value of 7.0. By substituting the carbon source in the medium with biowastes from different industries, the maximal production of PHA was 2.5 mg/ml PHA from 10% sugarcane molasses at the neutral pH range. The PHA produced in all the other industrial wastes was not comparable with that of sugarcane molasses. Hence, it can be concluded that sugarcane molasses can be used as a cheap source of carbon and is economical for the production of PHA on a large-scale.
Production and Optimization of Polyhydroxyalkanoate from Oleaginous Bacteria Bacillus Sp. ISTC1
Research & Reviews: Journal of Microbiology and Biotechnology, 2016
The present effort involved isolation and screening of bacterial strain Bacillus sp. ISTC1 for production of PHA and optimization of selected process parameters for enhanced production of PHA and biomass. Screening of selected bacterial strain for PHA production was based on Nile red staining, fluorescence microscopic visualization, spectrofluorometric measurement of Nile red fluorescence of the bacterial culture having 0.5% (w/v) glucose as carbon source. The presence of 3-hydroxyvalerate revealed by GC–MS served as a confirmatory analysis of PHA accumulation. Detection of characteristic functional group by FT-IR further confirmed the production of PHA by the bacterium. Response Surface Methodology (RSM) was used for optimization of pH, time duration and carbon source concentrations for an increased PHA production. On equating the optimized condition with the pre-optimized one, there was almost a 60% increase in the production of PHA. Therefore the finding thus established the production of PHA by Bacillus sp. ISTC1.
Journal of basic microbiology, 2018
Mixed bacterial cultures are increasingly being used in the production of polyhydroxyalkanoates (PHAs), as they have the potential to be more cost effective than axenic pure cultures. The purpose of this study was to use pure cultures in combination to identify their potential of PHA production. In this work we used volatile fatty acids (VFAs) and glucose as carbon source to check the ability of selected strains ST2 (Pseudomonas sp.) and CS8 (Bacillus sp.) as co-culture. The production of PHA in pure co-cultures of bacteria was therefore investigated in order to understand the effect of combining cultures on PHA production parameters and material properties. Bacteria could use the feed in better way when mixed as compared to individual strain. In undertaking this analysis, model volatile fatty acids (i.e., acetic and propionic acids) were used alone and in combination with glucose as feedstock. The production by Pseudomonas was 34% while 24% by Bacillus. However when combined and mi...
Food waste conversion to microbial polyhydroxyalkanoates
Microbial biotechnology, 2017
Polyhydroxyalkanoates (PHAs) are biopolymers with desirable material properties similar to petrochemically derived plastics. PHAs are naturally produced by a wide range of microorganisms as a carbon storage mechanism and can accumulate to significantly high levels. PHAs are an environmentally friendly alternative to their petroleum counterparts because they can be easily degraded, potentially reducing the burden on municipal waste systems. Nevertheless, widespread use of PHAs is not currently realistic due to a variety of factors. One of the major constraints of large-scale PHA production is the cost of carbon substrate for PHA-producing microbes. The cost of production could potentially be reduced with the use of waste carbon from food-related processes. Food wastage is a global issue and therefore harbours immense potential to create valuable bioproducts. This article's main focus is to examine the state of the art of converting food-derived waste into carbon substrates for mi...
Biofuels, Bioproducts and Biorefining, 2018
Polyhydroxyalkanoates (PHAs) are a family of biodegradable intracellular polyesters that a number of Eubacteria and Archaea can accumulate for energy and carbon storage. Most of the genetic modifications to the producing bacterial species have been accomplished to clarify basic biochemical, genetic, and metabolic aspects of PHA metabolism. However, due to its plastic-like properties and complete biodegradability, this bio-based polymer has attracted the attention of a variety of manufacturers. A number of genetic approaches have therefore been reported, aimed at improving the performance of the microorganisms with a potential for use in a production process. Indeed, genetic tools may find useful applications in all the phases of the PHA production chain, from the isolation and characterization of new microbial strains through all the production steps until they reach the downstream processes. The substrates generally used for PHA production are expensive, so the search for low-cost feedstock is necessary. These materials, possibly deriving from agri-food processes, are unfortunately not easily degraded or converted directly into PHAs. Thus, the development of engineered microbes is in progress to process waste streams and covert them to valuable polymers. This review will summarize the most relevant results obtained through genetic engineering tools for the production of PHAs from cheap carbon sources in view of possible industrial applications.
Advances in Polyhydroxyalkanoate (PHA) Production, Volume 2
Bioengineering, 2020
During the two years that have passed since the first volume of “Advances in Polyhydroxyalkanoate (PHA) production” was published, the progress in PHA-related research was indeed tremendous, calling for the next, highly bioprocess- and bioengineering-oriented volume. This editorial paper summarizes and puts into context the contributions to this second volume of the Bioengineering Special Issue; it covers highly topical fields of PHA-related R&D activities, covering, beside the pronounced bioengineering-related articles, the fields of the microbiology of underexplored, but probably emerging, PHA production strains from the groups of Pseudomonas, cyanobacteria, methanotrophs, and from the extremophilic domain of haloarchaea. Moreover, novel second-generation lignocellulose feedstocks for PHA production from agriculture to be used in biorefinery concepts, new approaches for fine-tuning the composition of PHA co- and terpolyesters, process simulation for PHA production from methane-ric...
Process Design and Evaluation of Biobased Polyhydroxyalkanoates (pha) Production
Chemical engineering transactions, 2011
Conventional plastic products are made of crude oil components through polymerization. Aim of the project ANIMPOL is to convert lipids into polyhydroxyalkanoates (PHA) which constitute a group of biobased and biodegradable polyesters. Replacing fossil based plastics with biobased alternatives can help reducing dependence on crude oil and decrease greenhouse gas emissions. As substrate material waste streams from slaughtering cattle, pig or poultry are taken into account. Lipids from rendering site are used for biodiesel production. Slaughtering waste streams may also be hydrolyzed to achieve higher lipid yield. Biodiesel can be separated into a high and low quality fraction. High quality meets requirements for market sale as fuel and low quality can be used for PHA production. This provides the carbon source for PHA production. Nitrogen source for bacteria reproduction is available from hydrolyzed waste streams or can be added separately. Selected microbial strains are used to produ...