Improved productivity of poly (3-hydroxybutyrate) (PHB) in thermophilic Chelatococcus daeguensis TAD1 using glycerol as the growth substrate in a fed-batch culture

Abstract

A particularly successful polyhydroxyalkanoate (PHA) in industrial applications is poly (3-hydroxybutyrate) (PHB). However, one of the major obstacles for wider application of PHB is the cost of its production and purification. Therefore, it is desirable to discover a method for producing PHB in large quantities at a competitive price. Glycerol is a cheap and widely used carbon source that can be applied in PHB production process. There are numerous advantages to operating fermentation at elevated temperatures; only several thermophilic bacteria are able to accumulate PHB when glycerol is the growth substrate. Here, we report on the possibility of increasing PHB production at low cost using thermophilic Chelatococcus daeguensis TAD1 when glycerol is the growth substrate in a fed-batch culture. We found that (1) excess glycerol inhibited PHB accumulation and (2) organic nitrogen sources, such as tryptone and yeast extract, promoted the growth of C. daeguensis TAD1. In the batch fermentation experiments, we found that using glycerol at low concentrations as the sole carbon source, along with the addition of mixed nitrate (NH4Cl, tryptone, and yeast extract), stimulated PHB accumulation in C. daeguensis TAD1. The results showed that the PHB productivity decreased in the following order: two-stage fed-batch fermentation > fed-batch fermentation > batch fermentation. In optimized culture conditions, a PHB amount of 17.4 g l(-1) was obtained using a two-stage feeding regimen, leading to a productivity rate of 0.434 g l(-1) h(-1), which is the highest productivity rate reported for PHB to date. This high PHB biosynthetic productivity could decrease the total production cost, allowing for further development of industrial applications of PHB.

Production of Polyhydroxyalkanoate (PHA) Biopolyesters by Extremophiles?

“…Based on these batch-results, fedbatch and two-stage fedbatch cultivation techniques were developed. In the two-stage fedbatch process, best results for PHB concentration (17.4 g/L), corresponding to a volumetric productivity of 0.434 g/(L.h), which is the currently highest PHA productivity reported for extremophiles, were obtained [109].…”

Production of polyhydroxybutyrate and alginate from glycerol byAzotobacter vinelandiiunder nitrogen-free conditions

“…Although A. vinelandii grown on glucose together with nitrogen sources synthesizes much PHB (74% per dry cell), 35 and some bacteria such as Burkholderia cepacia, 36 Chelatococcus daeguensis, 37 Cupriavidus necator (formerly Ralstonia eutropha), 38,39 Paracoccus denitrificans, 40 Pseudomonas oleovorans, 41 and Zobellella denitrificans, 42 have also been known to produce PHB from glycerol with nitrogen sources, the bacterial production of PHB from glycerol without a nitrogen source contributes to green chemistry.…”

Enhanced trans‐2,3‐dihydro‐3‐hydroxyanthranilic acid production by pH control and glycerol feeding strategies in engineered Pseudomonas chlororaphis GP72

“…Several reports have explored the utilization of glucose as a carbon source to produce phenazine by different Pseudomonas strains. However, it was not considered a sustainable raw feedstock for commercial‐scale productions due to its higher price . Glycerol generated as a waste during biodiesel production has become an easily available and low‐priced carbon source for producing high‐value products .…”

“…In contrast, alkaline pH slightly diminished the DHHA production, since elevated pH could be more effective in neutralizing the acidity generated during the fermentation bioprocess as reported earlier. 30,31…”