バイオテクノロジーとバイオマテリアル

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Bioethanol Production by an Ethanol-Tolerant Bacillus cereus Strain GBPS9 Using Sugarcane Bagasse and Cassava Peels as Feedstocks

Victor Ezebuiro, Chimezie Jason Ogugbue, Boma Oruwari and Francis Sopuruchukwu Ire

Bioethanol production potential of ethanol-tolerant Bacillus cereus strain GBPS9 using sugarcane bagasse and cassava peels as feedstocks was investigated. The Bacillus cereus GBPS9 used in this study was isolated from agro-wastes impacted soil and classified based on phylogenetic analysis of its 16S rRNA gene. The sequence of the isolate has been deposited in GenBank under the accession number KT318371.1. The isolate was selected based on its cellulolytic ability, tolerance to ethanol concentration of 6% (v/v) and ability to ferment sugar to ethanol. The substrates employed in the study were cassava peels and sugarcane bagasse. Chemical composition analysis showed total carbohydrate and lignin contents (% dry weight) of 69.6 ± 1.2 and 13.9 ± 0.4 for cassava peels and 70.3 ± 1.9 and 16.2 ± 1.2 for sugarcane bagasse, respectively. The feedstocks were subjected to acid, alkali and steam explosion pretreatments to increase cellulose content and therefore, reduce lignin content. The best pretreatment methods (steam explosion for sugarcane bagasse and acid for cassava peels) increased total carbohydrate contents to 85.4 ± 2.33 and 80.4 ± 2.5 for sugarcane bagasse and cassava peels, respectively. The respective lignin contents after pretreatment were 4.2 ± 0.44 and 4.8 ± 0.8 for sugarcane bagasse and cassava peels. Cultural conditions (pH, temperature, nitrogen source, inoculum size and substrate concentration) of the bacterium were optimized to enhance cellulase production. The laboratory scale fermentation of the feedstocks to ethanol was carried out in 250 mL Erlenmeyer flasks. Gas Chromatography – Mass spectrometry (GC-MS) analysis of the fermentation broth of sugarcane bagasse and cassava peels substrates revealed ethanol contents of 18.40 and 17.80 g/L, respectively. The study has demonstrated efficient bioethanol production by Bacillus cereus GBPS9 using sugarcane bagasse and cassava peels as feedstocks.