Enhancement Of Glucose Yield From Cellulose Enzymatic Sacchariifcation By Bio-pretreatment Of Bamboo

Lignocellulosic biomass, mainly from agricultural residues and forestry sources, is themost promising alternative source for ethanol production as it is sufficiently abundant andwidespread. Bamboo, as one of the most abundant cellulosic materials in China, has greatpotential to be used for ethanol production. The complex structure of native lignocellulosicbiomass, however, is highly resistant to enzymatic hydrolysis, resulting in low celluloseconversion. Therefore, a pretreatment process is needed to reduce the biomass recalcitrance bybreaking lignin seals and disrupting the crystalline structure of cellulose for improvingenzymatic hydrolysis. This paper focused on the fungal pretreatment for bamboos to enhancethe glucose yield of enzymatic hydrolysis.Four common Chinese bamboos, Neosinocalamus affinis, Bambusa rigida Keng et Kengf., Dendrocalamus yunnanicus and Bambusa pervaniabilis were biopretreated by six speciesfungus, Gloeophyllum trabeum (Pers.) Murrill, Coriolus versicolor, Postia placenta,Cheatomium globosum, Trametes versicolor and Phanerochaete chrysosphorium. In order tofound out the best pretreatment contions which leads to the maximum glucose yield, the testwas taken under different pretreated time, hydrolysis time and medium (Sand&dust mediumand Potato dextrose agar medium). The main conclusions as following:The optimum bio-pretreatment conditions for bamboo:(1) Both the G. trabeum and T.versicolor could enhance the enzymatic hydrolysis of bamboo, and the pretreatment efficiencyof T. versicolor was better. The enhancement of Coriolus versicolor, Postia placenta,Cheatomium globosum and Phanerochaete chrysosphorium were not obvious.(2) For the fourtested bamboos, the pretreatment method that fungus cultured on Sand&dust medium had2to8percent more glucose yield than that on Potato dextrose agar medium, and the maximumglucose yield was about26%from D. yunnanicus.(3) The optimum pretreatment time of T.versicolor and G. trabeum were28and42days respectively. The optimum technological conditons was when bamboo is pretreated by T. versicolor cultured on Sand&dust medium for28days and then hydrolysised by20FPU/g cellulase for48hours.The effect of physical properties on glucose yield:(1) The properties of bamboos werewidely different from each other. The density of four bamboos in this experiement were among0.58~0.60g/cm3. The crystallinity were among39.69%~52.05%, and B. rigida＞N. affinis＞B. pervaniabilis＞D. yunnanicus. The fiber tissue ratios were among38.47%~44.05%, and N.affinis＞B. rigida＞B. pervaniabilis＞D. yunnanicus.(2) In order of natural decay resistanceof the four bamboos, it gone: N. affinis, B. rigida, D. yunnanicus, B. pervaniabilis. For thosefour bamboos, greater density, larger crystallinity and higher fiber tissue ratios lead to lessweight loss what meant greater natural dacay resistance. The greater decay resistance bamboowas, the less glucose yield bamboo had.(4) In order to got more glucose yield, it was better tochoose bamboo that was less dense, crystallinity, fiber tissue retio and lower decay resistanceas the raw materials for biopretreatment.The chemical and physical changes of bamboo during biopretreatment:(1) The weightloss increased and crystallinity decreases with pretreatment time.(2) The bamboo’s relativechanges in the ratios of lignin reference band with carbohydrate associated bands forNeosinocalamus affinis decreased when pretreated by T. versicolor and increased by G.trabeum.(3) The cellulose and lingin content of pretreated bamboos became less with thepretreated time. And the T. versicolor lead to more lingin loss than G. trabeum.(4) T. versicolorcould degrade the main three main component and G. trabeum mainly degrade holocellulose.(5) The lingin would obstacles the enzymatic hydrolysis and the glucose yield was negativelyrelated to the lingin content by the linear regression analysis.(6) In order to got more glucoseyield, it was better to choose fungus which has the ability to degrade bamboo lignin andselectivity value of lignin degradation.The comparation of chemical pretreatment and biopretreatment:(1) NaOH had greatdelignification ability and results in decline of crystalinity. H2SO4mainly resolved celluloseand results in increase of crystalinity.(2) The residue from enzymatic hydrolysis had differentlingin content. When bamboo was pretreated by NaOH, the residue had the most lingin. When pretreated by T. versicolor and G. trabeum, the residue had the minimum lingin content. SoNaOH lead to hydrolysis more completely.(3) The main component of hydrolysate wereglucose and xylose. The maximum glucose concentration was18.196g/L coming fromhydrolysate pretreated by NaOH, the second was9.336g/L by H2SO4, the third was3.004g/Lby T. versicolor, and the last was1.952g/L by G. trabeum.(4) The advantages of fungalpretreatment was low energy requirement and mild environmental conditions. But processingcycles was much longer than chemical pretreatment.