Jong-il Choi

Recent advances in polyhydroxyalkanoate production by bacterial fermentation: mini-review

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.

Efficient and economical recovery of poly(3‐hydroxybutyrate) from recombinant Escherichia coli by simple digestion with chemicals

2/kg) similar to that of other biodegradable polymers under development.

Production of medium-chain-length polyhydroxyalkanoates by high-cell-density cultivation of Pseudomonas putida under phosphorus limitation.

A simple method for the recovery of microbial poly(3-hydroxybutyrate) [P(3HB)] from recombinant Escherichia coli harboring the Ralstonia eutropha PHA biosynthesis genes was developed. Various acids (HCl, H2SO4), alkalies (NaOH, KOH, and NH4OH), and surfactants (dioctylsulfosuccinate sodium salt [AOT], hexadecyltrimethylammonium bromide [CTAB], sodium dodecylsulfate [SDS], polyoxyethylene-p-tert-octylphenol [Triton X-100], and polyoxyethylene(20)sorbitan monolaurate [Tween 20]) were examined for their ability to digest non-P(3HB) cellular materials (NPCM). Even though SDS was an efficient chemical for P(3HB) recovery from recombinant E. coli, it is expensive and has waste disposal problem. NaOH and KOH were also efficient and economical for the recovery of P(3HB), and therefore, were used to optimize digestion condition. When 50 g DCW/L of recombinant E. coli cells having the P(3HB) content of 77% was treated with 0.2 N NaOH at 30 degrees C for 1 h, P(3HB) was recovered with purity of 98.5%. Using this simple recovery method, the effect of recovery method on the final production cost of P(3HB) was examined. Processes for the production of P(3HB) by recombinant E. coli from glucose with two different recovery methods, surfactant-hypochlorite digestion and simple digestion with NaOH, were designed and analyzed. By employing the fermentation process that resulted in P(3HB) concentration, P(3HB) content and P(3HB) productivity of 157 g/L, 77%, and 3.2 P(3HB) g/L-h, respectively, coupled with the recovery method of NaOH digestion, the production cost of P(3HB) was US

Production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) by high-cell-density cultivation of Aeromonas hydrophila

3.66/kg P(3HB), which was 25% less than that obtained by employing the surfactant-hypochlorite digestion method.

Effect of fermentation performance on the economics of poly(3-hydroxybutyrate) production byAlcaligenes latus

High-cell-density fed-batch cultures of Pseudomonas putida were carried out for the production of medium-chain-length polyhydroxyalkanoates (PHAs) using oleic acid as a carbon source. By employing an optimal feeding strategy without the limitation of any nutrient, a high cell concentration of 173 g/L was achieved, but the PHA concentration and PHA content were only 32.3 g/L and 18.7 wt%, respectively. To increase the PHA concentration and content, phosphorus limitation was applied during fed-bath culture by reducing the initial KH(2)PO(4) concentration. When the initial KH(2)PO(4) concentration was reduced to 4 g/L, cell concentration, PHA concentration, and PHA content obtained in 38 h were 141 g/L, 72. 6 g/L, and 51.4 wt%, respectively, resulting in a high productivity of 1.91 g PHA/L per hour.

Display of Bacterial Lipase on the Escherichia coli Cell Surface by Using FadL as an Anchoring Motif and Use of the Enzyme in Enantioselective Biocatalysis

The newly screened Aeromonas hydrophila produces copolymer consisting of 3-hydroxybutyrate (3HB) and 3-hydroxyhexanoate (3HHx). The characteristics of cell growth and polymer accumulation were examined using various carbon sources. P(3HB-co-3HHx) was produced from lauric acid and oleic acid only. P(3HB-co-3HHx) content can be increased by limitation of phosphorus. A maximal P(3HB-co-3HHx) content of 28.8 wt% could be obtained in flask culture. By applying the optimally designed nutrient feeding strategy, cell dry weight, P(3HB-co-3HHx) content, and 3HHx fraction obtained over the course of 43 h were 95.7 g/L, 45.2 wt%, and 17 mol%, respectively, resulting in a productivity of 1.01 g polyhydroxyalkanoate (PHA)/L. h.

Production of Microbial Polyester by Fermentation of Recombinant Microorganisms

The effects of fermentation performance on the final production cost of poly(3-hydroxybutyrate) [P(3HB)] were examined. Two processes for the production of P(3HB) byAlcaligenes latus from sucrose with the recovery method of surfactant-hypochlorite digestion were designed and subsequently analysed. The actual fermentation results that were different in the final P(3HB) content, P(3HB) yield and P(3HB) productivity were used in the simulations. The production cost of P(3HB) was significantly lower with higher P(3HB) content due to the reduction in polymer recovery cost. The cost of raw materials (mainly sucrose) was also lower with higher P(3HB) content since the process yielding higher P(3HB) content also resulted in higher P(3HB) yield on carbon source. The direct fixed capital-dependent costs decreased with increasing productivity. By employing the fermentation process that resulted in high P(3HB) concentration, P(3HB) content and P(3HB) productivity of 98.7 g/l, 88.3% and 4.94 g P(3HB)/l/h, respectively, the final production cost of P(3HB) was as low as US

Production and degradation of polyhydroxyalkanoates in waste environment

2.6/kg P(3HB).

High level production of supra molecular weight poly (3-hydroxybutyrate) by metabolically engineeredEscherichia coli

ABSTRACT We have developed a novel cell surface display system by employing FadL as an anchoring motif, which is an outer membrane protein involved in long-chain fatty acid transport in Escherichia coli. A thermostable Bacillus sp. strain TG43 lipase (44.5 kDa) could be successfully displayed on the cell surface of E. coli in an active form by C-terminal deletion-fusion of lipase at the ninth external loop of FadL. The localization of the truncated FadL-lipase fusion protein on the cell surface was confirmed by confocal microscopy and Western blot analysis. Lipase activity was mainly detected with whole cells, but not with the culture supernatant, suggesting that cell lysis was not a problem. The activity of cell surface-displayed lipase was examined at different temperatures and pHs and was found to be the highest at 50°C and pH 9 to 10. Cell surface-displayed lipase was quite stable, even at 60 and 70°C, and retained over 90% of the full activity after incubation at 50°C for a week. As a potential application, cell surface-displayed lipase was used as a whole-cell catalyst for kinetic resolution of racemic methyl mandelate. In 36 h of reaction, (S)-mandelic acid could be produced with the enantiomeric excess of 99% and the enantiomeric ratio of 292, which are remarkably higher than values obtained with crude lipase or cross-linked lipase crystal. These results suggest that FadL may be a useful anchoring motif for displaying enzymes on the cell surface of E. coli for whole-cell biocatalysis.

Pilot scale production of poly(3-hydroxybutyrate-co-3-hydroxy-valerate) by fed-batch culture of recombinantEscherichia coli

Polyhydroxyalkanoates (PHAs) can be produced from renewable sources and are biodegradable with similar material properties and processibility to conventional plastic materials. With recent advances in our understanding of the biochemistry and genetics of PHA biosynthesis and cloning of the PHA biosynthesis genes from a number of different bacteria, many different recombinant bacteria have been developed to improve PHA production for commercial applications. For enhancing PHA synthetic capacity, homologous or heterologous expression of the PHA biosynthetic enzymes has been attempted. Several genes that allow utilization of various substrates were transformed into PHA producers, or non-PHA producers utilizing inexpensive carbon substrate were transformed with the PHA biosynthesis genes. Novel PHAs have been synthesized by introducing a new PHA biosynthesis pathway or a new PHA synthase gene. In this article, recent advances in the production of PHA by recombinant bacteria are described.