Industrial production of PHA

PH As discovered by Lemoigne [23] more than 70 years ago. The P(3HB) is produced and stored inside the bacterial cell walls in granules. Alcaligenes eutrophus, which was the first strain used for the semi-industrial production of PHAs, can accumulate large quantities of P(3HB) as discrete intercellular granules by careful control of the fermentation process, i.e., up to 80% of the weight of the dried cell can be in the form of P(3HB) granules [7]. 

Industrial Production of PHAs History and Current Landscape... 

Chen GQ (2009b) Industrial production of PHA. Microbiol Monogr. doi 10.1007/978-3-642-03287-5 6... 

Figure 3.6 Strain and process deveiopment for industrial production of PHAs. (Ref. [60], reprinted with permission of ACS Pubiications.)...

The industrial production of PHA is already a reality, but the utilization of pure nficrobial cultures leads to high production costs, making the final product significantly expensive compared to conventional thermoplastics. For this reason, efforts are made to create PHA through economical production strategies, using mixed microbial cultures (Fradinho et al. 2013). 

Economic evaluation of the bacterial process for poly(3HB) production suggests that the cost of the carbon substrate accounts for up to 50 % of the total cost of poly(3HB) production (Choi and Lee 1997). A successful bacterial process for PHA production hence depends on the availability of a low-cost carbon substrate. Besides carbohydrates, organic acids and short-chain alcohols are also potential carbon substrates for the industrial production of PHAs. The cellular toxicity of the latter compounds, however, requires the isolation or identification of PHA producers that are more tolerant to these compounds. Reported progress includes the production of PHAs from whey or acetic and butyric acids. 

An alternative to the extraction of intact PHA polymer is the isolation of PHA monomers, oligomers, or various derivatives such as esters [74]. PH As are composed of stereo-chemically pure P-3-hydroxyacids, and therefore can be used as a source of optically pure organic substrates for the chemical and pharmaceutical industry [79]. In this protocol, the defatted cake containing PHA polymer would be chemically treated to obtain the PHA derivatives. For example, transesterification of the meal with methanol would give rise to methyl esters of 3-hydroxyalkanoic acids. The PHA derivatives would then be separated from the meal with appropriate solvents. One potential disadvantage of this method is the potential alteration of the quality of the residual meal if the harsh chemical treatments required for the production of PHA derivatives lead to protein or amino acid breakdown. 

For large-scale recombinant production of bacterial polymers, non-polymer producing bacteria were exposed to biosynthesis pathways. Polymers such as PHA, CGP (cyanophycin granule peptide), HA (hyaluronic acid), and PGA [poly-y-glutamate] were produced by these methods [89, 85-96]. For example, recombinant E.coli [89] was fermented for the lai e-scale production of PHA [89]. In addition the PHB biosynthesis genes of Ralstonia eutropa were harbored in E.coli to produce poljmers such as PHA composed of (R)-S-hydroxybutyrate and (R)-3-hydroxyvalerate and/or (R)-3-hydroxyhexanoate which showed preferable properties for use in industrial applications [97-99, 85-96]. 

Poly(hydroxyalkanoates) (PHAs) are a very common class of bacterial reserve materials, that have attracted considerable industrial attention (Anderson and Dawes, 1990). These polyesters are biodegradable and biocompatible thermoplastics with physical and mechanical properties dependent on their monomeric composition. The production of PHAs is a typical biotechnological process whose development requires the involvement of several scientific disciplines, i.e. genetics, biochemistry, microbiology, bioprocess engineering, polymer chemistry, and polymer engineering. 

Abstract Many types of fermentation feedstock have been studied for the production of polyhydroxyalkanoate (PHA). Several industrial-scale processes have been developed for PHA production from sugars. Sugars are attractive feedstock because of their abundant supply worldwide, market stability, and also because the metabolism of PHA from sugars is very well understood. Recently, plant oils have been gaining much interest as a potential feedstock for PHA production. Industrial-scale processes for the production of PHA from plant oils are currently being developed. This chapter looks at the challenges in using plant oils, especially pahn oil as feedstock for PHA production. 

Abstract Polyhydroxyalkanoate (PHA) initially received serious attention as a possible substitute for petrochemical-based plastics because of the anticipated shortage in the supply of petroleum. Since then, PHA has remained as an interesting material to both the academia and indusby. Now, we know more about this microbial storage polyester and have developed efficient fermentation systems for the large-scale production of PHA. Besides sugars, plant oils will become one of the important feedstock for the industrial-scale production of PHA. In addition, PHA will find new apphcations in various areas. This chapter summarizes the future prospects and the importance of developing a sustainable production system for PHA. 

Wastewater comprises liquid waste discharged by households, industries and commercial establishments, and is typically collected through sewage pipes in municipal areas. Wastewater also contains chemicals and pathogens that can lead to serious negative impacts on the quality of the environment as well as human health if it is drained directly into major watershed without treatment [4,5]. The use of wastewater as a feedstock in the production of PHA has been proposed as a relevant approach in the shift from a petrochemical-based chemical industry towards a biobased one in order to decrease its manufacturing cost and environmental impact [6]. 

The use of mixed microbial cultures and optimisation strategies in fermentations can be a viable strategy to obtain a high cell density for the improvement of PHA production at an industrial level. Therefore, further studies should be initiated in order to obtain higher productivity of PHA with an associated lower cost of production. 

Upstream PHA processing includes the production of PHA from cheap raw materials and emphasis has mainly been focused on renewable feedstocks (industrial waste and by-products). These feedstocks have been used to isolate new bacterial strains capable of utilising these compounds as substrates, followed by an extensive biosynthesis of PHA on various fermentation scales. Furthermore, genetic modification has been carried out on known PHA producers... 

Lactic acid is known to have numerous fields of industrial application, such as foods, cosmetics, pharmaceuticals, textiles and chemicals (Wee et al. 2006). Via simple chemistry, lactic acid can be converted into lactic acid esters that constitute so-called green solvents. In the area of polymers, lactic acid opens the route for the chemical production of PLA and the biotechnological production of PHA (see Fig. 6). 

However, the production of PHAs employing recombinant E. coli was restrained on both the laboratory scale and the industrial scale owing to low efficiency and high cost. 

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