Utilization of Sugarcane Bagasse by Halogeometricum borinquense Strain E3 for Biosynthesis of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Abstract

Sugarcane bagasse (SCB), one of the major lignocellulosic agro-industrial waste products, was used as a substrate for biosynthesis of polyhydroxyalkanoates (PHA) by halophilic archaea. Among the various wild-type halophilic archaeal strains screened, Halogeometricum borinquense strain E3 showed better growth and PHA accumulation as compared to Haloferaxvolcanii strain BBK2, Haloarcula japonica strain BS2, and Halococcus salifodinae strain BK6. Growth kinetics and bioprocess parameters revealed the maximum PHA accumulated by strain E3 to be 50.4 ± 0.1 and 45.7 ± 0.19 (%) with specific productivity (qp) of 3.0 and 2.7 (mg/g/h) using NaCl synthetic medium supplemented with 25% and 50% SCB hydrolysate, respectively. PHAs synthesized by strain E3 were recovered in chloroform using a Soxhlet apparatus. Characterization of the polymer using crotonic acid assay, X-ray diffraction (XRD), differential scanning calorimeter (DSC), Fourier transform infrared (FT-IR), and proton nuclear magnetic resonance (1H-NMR) spectroscopy analysis revealed the polymer obtained from SCB hydrolysate to be a co-polymer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] comprising of 13.29 mol % 3HV units.

A Review on Established and Emerging Fermentation Schemes for Microbial Production of Polyhydroxyalkanoate (PHA) Biopolyesters

“…In most cases, scl-PHA producing microbes convert simple carbon sources like sugars, alcohols or lipids via acetyl-CoA towards 3HB; production of 3HV or 4HB normally requires structurally related precursor substrates such as the 3HV-precursors propionic acid [27], valeric acid [28], levulinic acid [29][30][31], the cocktails of ozonolytically splitted fatty acids [32] or non-oxygenated polyethylene wax [33], or 4HB-precursors like γ-butyrolactone (GBL), 4HB sodium salt, or 1,4-butanediole [34,35]. Among extremophilic Archaea, a number of strains such as Haloferax mediterranei [36] or Halogeometricum borinquense [37] have been identified, which produce copolyesters of 3HB and 3HV (PHBHV) from simple, structurally unrelated substrates such as carbohydrates or glycerol, which in turn saves on precursor costs for copolyester synthesis. Among eubacteria, PHA copolyester production from unrelated substrates is a scarce feature and reported, e.g., for the Gram-positive strain Bacillus licheniformis PL26 [5] and the Gram-negative strain Hydrogenophaga pseudoflava [38].…”

Haloferax volcanii for biotechnology applications: challenges, current state and perspectives

“…H. volcanii produces PHB up to 7% of its cell dry weight when grown on media containing 250 g/L salts, 10 g/L glucose and 1 g/L yeast extract (Fernandez-Castillo et al 1986). An additional report for H. volcanii mediated PHA accumulation from sugarcane bagasse substrate, a fibrous leftover by-product of the sugarcane industry, was recently published (Salgaonkar and Bragança 2017). In contrast, another study reported no detection of PHB from H. volcanii (Legat et al 2010).…”

Chemical and Biochemical Engineering Approaches in Manufacturing Polyhydroxyalkanoate (PHA) Biopolyesters of Tailored Structure with Focus on the Diversity of Building Blocks

“…As demonstrated in the case of Hfx. mediterranei and Halogeometricum borinquense, such organisms produce poly(3HB-co-3HV) without the need for 3HV-related precursor compounds; feeding these strains with simple pure sugars, 116 hydrolyzed bagasse, 117 or glycerol 74 is sufficient to make them produce copolyesters. Only recently, copolyester production from inexpensive unrelated substrates was detected also in eubacteria, when Bacillus licheniformis PL26 was shown to accumulate poly(3HB-co-3HV) from crude glycerol from the biodiesel production.…”