Sustainable generation of bioethanol from sugarcane wastes by Streptomyces coelicolor strain COB KF977550 isolated from a tropical estuary

Abstract

The damaging effect and challenges associated with the use of fossil fuel is enormous and very costly. Biofuels could be obtained from plant biomass wastes which are known to be sources of environmental pollution and breeding grounds for vectors of diseases. Sugarcane bagasse was exploited as a renewable substrate for obtaining bioethanol using Streptomyces strain COB KF977550 as inoculum. Submerged aerobic batch fermentation was performed in flasks containing mineral salts medium supplemented with 5.0 g (w/v) sugarcane bagasse. Incubation was done in a shaker (150 rpm) at 30 oC for 21 days. Microbial growth was assessed by measurement of the optical density (O.D 600nm) at 3-day intervals. Fractional distillation was carried out in batch mode using a simple fractional distillation setup. Metabolic products were determined using GC-FID. Further analyses were performed using FTIR and GC-MS. The optical density of S.coelicolor strain COB KF977550 increased from 0.9 to 1.41. The GC-FID showed that 43.08 g/L ethanol was generated. Interestingly, the results showed the presence of diverse biochemicals released into the medium in addition to the main product ethanol. Ten carboxylic acids including formic acid, glycolic acid, tartaric acid, acetic acid, citric acid, oxalic acid, malic acid, lactic acid, n-valeric acid, and 3-hydroxybutyric acid were identified as biochemical organic acids by-products.