Investigation on Saccharification and Bioethanol Production from Pretreated Agro-Residues Using a Mangrove Associated Actinobacterium Streptomyces variabilis (MAB3)

The present study was undertaken to evaluate the saccharification, followed by bioethanol production by an actinobacterium Streptomyces variabilis (MAB3) isolated from the sediment sample of mangrove environment using Modified Yeast extract-Peptone medium substituted with different concentrations of xylanase (50 to 400 IU) pretreated various agro-residues like vegetable, banana, mango, sugarcane bagasse and sugarcane juice through fermentation process. Among the tested residues, sugarcane juice substituted medium pretreated with 200.0 IU concentration of xylanase exhibited maximum level of reducing sugar (50.19 mg/g), degree of saccharification (59.49%) as well as bioethanol (4.69 g/L) production. Further the organism expressed highest saccharification yield and bioethanol production at the optimized cultural conditions of pH 6, temperature 30 degrees C, inoculum size 2.5% and incubation time 72 h substituted with 2.5% dextrose and 2.0% urea, respectively as carbon and nitrogen sources. The concentration of produced bioethanol (82.26%) from the optimized medium was determined through HPLC analysis. Finally the bioethanol was evaluated through FT-IR and GC-MS analysis. The basic functional ethanol groups (O-H and C-O) from the optimized medium were denoted in both FT-IR and GC-MS analysis at the wavenumber of 3272.22 and 1077.15 cm(-1) with the retention time of 2.60 min, respectively. Based on the results, it could be confirmed that the selected isolate is a potent strain and it can able to hydrolyze the pretreated agro-residues and also it can able to convert the pretreated agro residues into economically important byproduct like bioethanol.