Enhanced Enzymatic Conversion Of Bamboo By Additive Addition

Moso Bamboo(Phyllostachys heterocycla var. Pubescens), as a fast growing, short renovation, and high contents of carbohydrates natural resource, has a great potential to be used as a fine feedstock for the production of biofuels. With the development of bamboo industry, more bamboo residues without fully utilized are produced. In addition, immature bamboo shoots gradually become uneatable due to high content of rough fiber,and cannot used as raw materials for manufacturing production. It is an efficient way to convert these wasted materials and bamboo shoot to fermentable sugars to produce ethanol or other chemicals. Pretreatment and enzymatic hydrolysis are the two main steps on bioethanol production from lignocellulosies.In this research, the performances of hot water, aqueous ammonia(SAA), dilute sulfuric acid(DA), and Na OH pretreatments were compared in pretreating bamboo for enzymatic hydrolysis. Besides, the synergistic effects between cellulases and xylanase on the hydrolysis of bamboo fractions and the effectiveness of additives(BSA, PEG 6000, Tween 80) on pretreatment and enzymatic saccharification of bamboo shoot and mature bamboo fractions(bamboo green, bamboo timber, bamboo yellow, bamboo node, and bamboo branches) by cellulases and/or xylanase were evaluated. The results were summarized as follows:1. Na OH and Tween 80-assisted Na OH pretreated bamboo showed the best delignification capacity(the removal of lignin were 54.2% and 57.9%, respectively), and the hydrolysis yield of pretreated bamboo was reached 85.6%. 39.5~45.6% of lignin were removed after SAA pretreatments, and the enzymatic digestibility was increased with the improvement of the pretreatment intensity. The maximum reducing sugar yield of SAA pretreated bamboo was 78%. DA pretreatment removed 67.3% of xylan, while only around 10% of lignin was removed, which resulted in the lowest hydrolysis yield(about 10%).2. The addition of Tween 80 on pretreatment had a negligible effect on the lignin removal of bamboo fractions, whereas Tween 80-assisted Na OH pretreated bamboo powder was easier to disperse in buffer than the sample with Na OH pretreated bamboo, which was beneficial for following operation of enzymatic hydrolysis, which might be due to the increase of hydrophilicity of bamboo surface by Tween 80. The highest sugar recovery(42.5 g/100 g DM of bamboo) was obtained from Tween 80 assisted Na OH pretreated bamboo hydrolyzed with CEL, XYL and Tween 80.3. The addition of additives on enzymatic hydrolysis could efficiently enhance the glucose and xylose release from different bamboo shoot and mature bamboo fractions. The addition of Tween 80 both before and after hydrolysis could increase the hydrolysis yields of bamboo, and the hydrolysis yields nearly leveled off when the concentration of Tween 80 above 150 mg/g DM. Tween 80 could enhance cellulose and xylan conversion with low cellulases loading, but under an opimal hydrolysis conditions the improvement by surfactant was limited.4. Supplementation of xylanase(1 mg/g DM) with cellulases(10 FPU/g DM) in the hydrolysis of bamboo fractions was more effective than the addition of additives in the production of glucose and xylose. Moreover, addition of additives could further increase the glucose release from different bamboo fractions by cellulases and xylanase. With the addition of cellulases, xylanase and additives, the hydrolysis yields of bamboo reached the maximum.5. Amost all of the polysaccharides in pretreated bamboo shoot fractions were hydrolyzed by cellulases with the addition of additives or xylanase which might because of the low lignifications of bamboo shoot. The highest hydrolysis yields of untreated bamboo shoot fractions could reach 70% and some contents of water-soluble sugars were contained, suggesting pretreatment was not necessary for the hydrolysis of bamboo shoot. Bamboo green exhibited the lowest hydrolyzability, which might because of the high density, hardness and lignin content.