Biosynthesis of Polyhydroxyalkanoates from Defatted Chlorella Biomass as an Inexpensive Substrate

Abstract

Microalgae biomass has been recently used as an inexpensive substrate for the industrial production of polyhydroxyalkanoates (PHAs). In this work, a dilute acid pretreatment using 0.3 N of hydrochloric acid (HCl) was performed to extract reducing sugars from 10% (w/v) of defatted Chlorella biomass (DCB). The resulting HCl DCB hydrolysate was used as a renewable substrate to assess the ability of three bacterial strains, namely Bacillus megaterium ALA2, Cupriavidus necator KCTC 2649, and Haloferax mediterranei DSM 1411, to produce PHA in shake flasks. The results show that under 20 g/L of DCB hydrolysate derived sugar supplementation, the cultivated strains successfully accumulated PHA up to 29.7–75.4% of their dry cell weight (DCW). Among the cultivated strains, C. necator KCTC 2649 exhibited the highest PHA production (7.51 ± 0.20 g/L, 75.4% of DCW) followed by H. mediterranei DSM 1411 and B. megaterium ALA2, for which a PHA content of 3.79 ± 0.03 g/L (55.5% of DCW) and 0.84 ± 0.06 g/L (29.7% of DCW) was recorded, respectively. Along with PHA, a maximum carotenoid content of 1.80 ± 0.16 mg/L was produced by H. mediterranei DSM 1411 at 120 h of cultivation in shake flasks. PHA and carotenoid production increased by 1.45- and 1.37-fold, respectively, when HCl DCB hydrolysate biotransformation was upscaled to a 1 L of working volume fermenter. Based on FTIR and 1H NMR analysis, PHA polymers accumulated by B. megaterium ALA2 and C. necator KCTC 2649 were identified as homopolymers of poly(3-hydroxybutyrate). However, a copolymer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 3-hydroxyvalerate fraction of 10.5 mol% was accumulated by H. mediterranei DSM 1411.

Biodegradable Polyurethanes Based on Castor Oil and Poly (3-hydroxybutyrate)

“…The PHB polymer used for the synthesis of end-capped PHB diols in this study was produced by Cupriavidus necator KCTC 2649 as previously described by Khomlaem et al [ 22 ]. Briefly, a minimal medium containing 1 g/L of (NH4) 2 SO 4 , 9 g/L of Na 2 HPO 4 × 12H 2 O, 1 g/L of MgSO 4 × 7H 2 O, 0.5 g/L of KH 2 PO 4 , 20 mg/L of CaCl 2 × 2H 2 O, 10 g/L of NaCl, and 2 mL/L of trace element solution supplemented with 20 g/L of glucose was used for C. necator KCTC 2649 cultivation in shake flasks.…”

Algae Based Bio-Plastics: Future of Green Economy

“…Chlorella pyrenoidosa was the strain under study in Fogg's medium with 80 Lux light intensity and UV spectroscopy analysis confirms PHB accumulation [26]. Since microalgae are low-cost substrate, Khomlaem et al [27] used defatted Chlorella biomass and used as a substrate for three bacterial strains to accumulate PHAs. Cupriavidusnecator, a bacterial strain employing 75.4 percent defatted chlorella biomass, demonstrated the highest PHA accumulation (7.51 + 0.20 g/L) among the studied strains [27].…”

“…Since microalgae are low-cost substrate, Khomlaem et al [27] used defatted Chlorella biomass and used as a substrate for three bacterial strains to accumulate PHAs. Cupriavidusnecator, a bacterial strain employing 75.4 percent defatted chlorella biomass, demonstrated the highest PHA accumulation (7.51 + 0.20 g/L) among the studied strains [27]. Another analysis revealed that adding glycerol as a plasticiser with defatted Chlorella biomass (DCB) to make Chitosan-based biodegradable films improved mechanical characteristics.…”

Microalgal Biomass as Feedstock for Bacterial Production of PHA: Advances and Future Prospects

“…as feedstock for PHB production ( Azizi et al, 2017 ). C. necator KCTC 2649 was able to produce 75.4 wt% of CDW of PHA by using 10% (w/v) of defatted Chlorella biomass ( Khomlaem et al, 2021 ). Likewise, C. necator TISTR 1335 was fed a combination of Chlorella sp.…”

“…LL1 was able to synthesize PHA as well as carotenoids ( Muhammad et al, 2020 ). Fascinatingly, this same species was able to utilize defatted Chlorella biomass to produce 37.4 wt% of CDW of PHA and 6.08 mg·L −1 of carotenoids ( Khomlaem et al, 2021 ). These findings highlight the compatibility of using microalgal biomass as feedstock for PHA production in Paracoccus.…”