Evaluation of polyhydroxyalkanoate (PHAs) production with a bacterial isolate using cassava flour hydrolysates as an alternative substrate

Abstract

In the production of polyhydroxyalkanoates (PHA), the costs of the process are mainly associated with the carbon source and most of the production studies are carried out with commercial strains. In this study, PHA production was evaluated using a strain, SB-34, compared with a referenced strain, Ralstonia eutropha H16, growing in cassava flour hydrolysates as an alternative carbon source. SB-34 reached a biomass maximum of 5,49 ± 0,21 g / L, and PHA product of 3,23 ± 0,21 g / L exceeding the maximum values obtained by R. eutropha H16 (3,8 ± 0,45 g / L and 2,42 ± 0,23 g / L, respectively). Analyzes with FTIR indicate that the polymer obtained with SB-34 is like polyhydroxybutyrate P(3-HB) type. Molecular analysis identified SB-34 as Burkholderia sp. with 96 % of similarity.

Green synthesis of polyhydroxyalkanoate polymer by Bacillus iocasae

“…for the bacterial isolate to force the bacteria to produce more PHAs. 8 A negative control was carried out besides the enhancement experiments.…”

“…1,[5][6][7] Additionally, PHAs can be converted into nano-sized particles for nano-based drug delivery. 2 The formation of the polymer is mainly associated with the stationary phase of many bacterial strains such as Bacillus cereus, Bacillus subtilis, Brevibacterium halotolerance and Pseudomonas aeruginosa [8][9][10] ; acetyl coenzyme A (acetyl-CoA), the intermediate of the central carbon metabolism, is required for cell synthesis during the exponential phase but is diverted to produce PHAs in the stationary phase. 11 PHA granules are made up of a hydrophobic, amorphous polymeric core enclosed by a single layer of phospholipids as well as protein molecules.…”

Limitations on production methods for PHAs obtention: a systematic review

“…Visualization of maximum productivity (Y axis), for the 5 species with the highest productivity found (Z axis), categorized by type of system and induction used (X axis), Source: The Authors. single reactor could be carried out [24]. Therefore, more research should be carried out in this field, since as mentioned, this cultivation system would improve productivity and competitiveness.…”

“…This bacterium is the most studied in the production of PHAs, since it is easy to grow, is not pathogenic for humans and it grows rapidly in simple sugars, additionally it can accumulate up to 90% dry polymer weight, and has the capacity to produce it in growth-associated and not associated [24]. The two highest productivity in this species were reported using glucose as a substrate (Table 2) and the third-largest using organic acids as a substrate (Fig.…”

“…In addition to the above, it should also be considered that continuous systems operated in cascade are more likely to become contaminated due to the multiple connections between each reactor; alternatively, the tubular flow piston reactors (CPFTR), can also be divided into several stages with different culture conditions, with the advantage that they allow to obtain higher product quality because the uniform physiological state of the cells can be kept, therefore they represent a promising and simpler alternative to operate [21]. C. necator production has also been reported growthassociated [24,35,40]. Alcaraz et al (2019) they evidenced that the formation of the polymer occurs from the growth stage due to an oxygen limitation in the culture, favoring the accumulation of PHA due to the increase of NADH in the cytoplasm, according to (Budde et al, 2010) [49], this accumulation inhibits the enzymes citrate synthase and isocitrate dehydrogenase, preventing acetyl-CoA from entering the tricarboxylic acid cycle.…”