Integration of poly-3-(hydroxybutyrate-co-hydroxyvalerate) production by Haloferax mediterranei through utilization of stillage from rice-based ethanol manufacture in India and its techno-economic analysis

Abstract

Haloferax mediterranei has potential for economical industrial-scale production of polyhydroxyalkanoate (PHA) as it can utilize cheap carbon sources, has capacity for nonsterile cultivation and allows simple product recovery. Molasses-based Indian distilleries are converting themselves to cereal-based distilleries. Waste stillage (14 l) of rice-based ethanol industry was used for the production of PHA by H. mediterranei in the simple plug-flow reactor configuration of the activated sludge process. Cells utilized stillage and accumulated 63 ± 3 % PHA of dry cell weight and produced 13.12 ± 0.05 g PHA/l. The product yield coefficient was 0.27 while 0.14 g/l h volumetric productivity was reached. Simultaneous lowering of 5-day biochemical oxygen demand and chemical oxygen demand values of stillage by 82 % was attained. The biopolymer was characterized as poly-3-(hydroxybutyrate-co-17.9 mol%-hydroxyvalerate) (PHBV). Directional properties of decanoic acid jointly with temperature-dependent water solubility in decanoic acid were employed for two-step desalination of the spent stillage medium in a cylindrical baffled-tank with an immersed heater and a stirrer holding axial and radial impellers. 99.3 % of the medium salts were recovered and re-used for PHA production. The cost of PHBV was estimated as US$2.05/kg when the annual production was simulated as 1890 tons. Desalination contributed maximally to the overall cost. Technology and cost-analysis demonstrate that PHA production integrated with ethanol manufacture is feasible in India. This study could be the basis for construction of a pilot plant.

Production of Polyhydroxyalkanoate (PHA) Biopolyesters by Extremophiles?

“…mediteranneimediated PHA production has been further optimized by researchers all around the world. Whereas some of these groups focused on the application of inexpensive carbon feedstocks to safe substrate costs, such as whey permeate from dairy industry [12,13,48], rice-based ethanol stillage [49], extruded rice bran [50], enzymatically extruded starch [51], crude glycerol phase [28], olive mill waste water [52], vinasse [53], etc., others clarified the enzymatic and genetic background of PHA-synthesis [54][55][56][57] and in vitro degradation [58] by this organisms. Mathematic models of PHA-production [59], and kinetic studies of PHA and by-product synthesis and degradation [60] were reported for Hfx.…”

Current developments on polyhydroxyalkanoates synthesis by using halophiles as a promising cell factory

“…When stillage was used to produce PHBV in a plug-flow reactor configuration of the activated sludge process, Hfx. mediterranei was able to accumulate 63% (wt) PHBV while 99.3% of the medium salt was recovered for re-use [66]. Additionally, the cost for 1890 tons of PHBV was estimated to be as low as US$ 2.05/kg.…”

Recent strategies for efficient production of polyhydroxyalkanoates by micro-organisms

“…On the other hand, PHAs can be advantageously synthesized at low cost when integrated into a related manufacturing unit such as sugarcane mill or ethanol industry (Bhattacharyya et al . , ), which made full use of instrumentation, materials and excess electricity from these industries. Establish a model with predictive power including mixed microbial cultures, mixed substrates uptake, process modelling and control and etc.…”