Pretreatment Of Hybrid Pennisetum And Its Enzymatic Hydrolysis Perfprmance

Energy grass is an attractive alternative material for production of bioenergy and biochemical due to their advantages of fast growth,high biomass,high photosynthetic efficiency,strong resistance,wide adaptability and high content of energy conversion components.In this paper,Hybrid Pennisetum was pretreated with aqueous ammonia,Na₂SO₃,NaOH and Na₂SO₃-NaOH to investigate the effects of various pretreatment on chemical composition,morphological structure and enzymatic digestibility.Besides,the synergistic effects between cellulases and xylanase on the hydrolysis of Hybrid Pennisetum and the relations between structure property and enzymatic digestibility were also investigated for the purpose of decreasing the the amount of cellulase and enhancing the hydrolysis yield of energy grass as possible as we can by addition of xylanase.The results were summarized as follows:1.After aqueous ammonia pretreatment at 70°C for 72 h,the amounts of lignin of Chinese Pennisetum and Hybrid Pennisetum decrease from 16.5%and 17.5%to 7.6%and11.8%and the cellulose content increased to 56.1%and 47.9%,respectively.Although crystallinity index?CI?of cellulose also decrease to some degree,the hydrolysability increased and Hybrid Pennisetum was better than Chinese Pennisetum.Supplementation of xylanase was more effective than increase of cellulases loading.After supplementation of 2mg of xylanase?XYL?/g dry matter?DM?to 5 FPU of cellulases/g dry matter,the hydrolysis yields of cellulose of aqueous ammonia pretreated Chinese Pennisetum and Hybrid Pennisetum were 92.3%⁹5.4%,and the hydrolysis yields of xylan were 86.9%⁹4.2%.2.Na₂SO₃ and Na₂SO₃-NaOH pretreatment led to lignin sulfonation,and the degree of sulfonation was enhanced with the dosage of Na₂SO₃ in Na₂SO₃ pretreatment but it has nothing to do with dosage of Na₂SO₃ in Na₂SO₃-NaOH pretreatment.Na₂SO₃ pretreatment resulted in higher elemental sulfur content?0.85%⁰.91%?,showed better hydrophilic property and worse hydrolysability compared to Na₂SO₃-NaOH pretreatment.Lower glucose yield?57.9%⁸6.5%?might be due to that higher lignin content and surface lignin content led to non-productive of cellulase with a greater degree.3.NaOH pretreatment was more effective in destroying the robust structure of Hybrid Pennisetum compared to Na₂SO₃ pretreatment.The addition of Na₂SO₃ in NaOH pretreatment could facilitate lignin removal?<5%?and prevent the degradation of cellulose and hemicellulose?⁹6%?.Na₂SO₃-NaOH pretreatment achieved 93%glucose yield and produced higher the amount of glucose?693.7 mg/g dry matter?and xylose?302.7 mg/g dry matter?.Both were 42%higher than those from NaOH-pretreated Hybrid Pennisetum.4.Cellulase loading of more than 10 FPU/g DM was not necessary for enzymatic hydrolysis of Na₂SO₃-,NaOH-and Na₂SO₃-NaOH-pretreated Hybrid Pennisetum.At lower substrate concentration,Na₂SO₃-NaOH pretreatment resulted in higher hydrolysability than Na₂SO₃ pretreatment,90%⁹3.6%and 57.9%and 86.5%,respectively.5.At 10%substrate concentration,addition of cellulase showed little effect on the increase of glucose yield,but xylanase addition clearly improved the hydrolysability.A glucose yield exceeding 94%?70 mg/mL?was obtained after supplementation of 10 FPU Celluclast 1.5 L/g DM,1000 nkat Novozyme 188/g DM with 2 mg xylanase/g DM.