Abstract
The aim of this study was to select the wild microorganism with the capacity to produce cellulases. Microbial sources were rotten grass, leaves and straws. Natural lignocellulose as the sole carbohydrate was used to enrich microorganisms. After isolation, the strains were inoculated into liquid media. Filter paper activity (FPA) was used as an index for selection. Sequencing of 26S rDNA D1/D2 region was used to identify the microorganism. Lactose, lactobionic acid, Tween 80 and yeast extract were added into cultivation system to improve FPA. Optimum temperature and pH of cellulase were investigated. After enrichment, isolation and selection according to FPA, one strain was selected. Trichoderma sp. A6 was named according to the sequencing results. When lactose (10 g/L) was added into the cultivation system, the FPA was improved from 0.16 to 0.56 IU. Lactose addition could improve FPA significantly. After addition, the FPA at two days amounted to the highest value. However, the addition of lactobionic acid did not increase FPA. Tween 80 addition only improved the FPA at four days to small extent. The 15 g/L yeast extract could increase the FPA at 2 days from 0.60 to 0.92 IU. The combination of Tween 80 and yeast extract did not improve the FPA compared with the treatment of Tween 80 addition. The optimum range of temperature and pH were 37-60 and 4.5-5.5°C, respectively. Key words: Cellulase, Trichoderma, selection, cultivation condition, optimization.
Highlights
Energy security, petroleum depletion, and global warming have become the main driving forces for developing renewable fuels that can replace petroleum-derived fuels.The renewable fuel expected to be widely used around globe is bioethanol, which is largely produced by fermenting starch- or sugar-containing feedstocks.the supply of these crops is relatively limited and many of them can be considered human food resources
It is known that the general process for converting lignocellulosic biomass into ethanol mainly includes feedstock pretreatment, enzymatic hydrolysis, sugars fermentation, separation of lignin residue, recovery and purifying the ethanol to meet fuel specifications
Culture supernatants obtained after centrifugation at 5800 × g for 10 min at 4°C were used to determine the filter paper activities (FPAs)
Summary
The renewable fuel expected to be widely used around globe is bioethanol, which is largely produced by fermenting starch- or sugar-containing feedstocks. The supply of these crops is relatively limited and many of them can be considered human food resources. Non-food crops will be more advantageous for bioethanol production (Alriksson et al, 2009; Sticklen, 2008). Lignocellulose is considered as one of the most important carbon sources on Earth and a less-expensive raw material with a great potential to produce energy. Lignocellulosic biomass used for producing ethanol has been a major focus (Lynd et al, 2008; Niranjane et al., 2007). It is known that the general process for converting lignocellulosic biomass into ethanol mainly includes feedstock pretreatment, enzymatic hydrolysis, sugars fermentation, separation of lignin residue, recovery and purifying the ethanol to meet fuel specifications
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