Research On The Enzymatic Hydrolysis Crafts Of Cellulose For Pennisetum Sp.

This paper studied the effect of three different preteatment methods, dilute acid pretreatment, dilute alkali pretreatment and biological pretreatment on the enzymolysis of Pennisetum sp. cellulose. Through determining the content of cellulose, hemicellulose, and lignin before and after the pretreatment process, the changes of sugar content in the enzymolysis liquid and cellulose structure, compared and analysed different pretreatment methods. The study provided a theoretical basis for Pennisetum sp. as bioethanol materials. The results were as follows:1. The text studied from four aspects of enzyme dosage, enzymolysis time, substrate concentration, buffer pH, reaction temperature to get optimal enzymolysis condition of Pennisetum sp.. According to the results obtained, the effect sequence of various factors was as follows:the enzyme dosage> enzymolysis time> substrate concentration> buffer pH> reaction temperature. The optimal enzymolysis condition was as follows, reaction time:60h, enzyme dosage:44.8u/g, substrate concentration:lOg/L, pH5.0, hydrolysis temperature:45℃. Under the optimal conditions, sugar content in enzymatic hydrolyzate was 102.656mg/g.2.Analysed the effect of solid liquid ratio, acid concentration, treatment time and temperature of dilute acid (H2SO4) on chemical composition of Pennisetum sp. and enzymatic hydrolysis reaction. Results showed that the dilute acid had obvious effect to degrade hemicellulose. Along with the acid concentration and the solid liquid ratio increasing, sugar content in liquid was growing, but it had smaller effect on the degradation of lignin. As the temperature and treatment time increasing, main chemical components and sugar content in liquid was changing, but from the point of view of reducing energy consumption, the best dilute acid (H2SO4) pretreatment condition was as follows, solid liquid ratio:1:20, acid concentration:2%, treatment time:60min and temperature:100℃.3. The text analysed the effect of solid liquid ratio, alkali concentration, treatment time and temperature of dilute alkali (NaOH) on chemical composition of Pennisetum sp. and enzymatic hydrolysis reaction. Results showed that the dilute alkali had obvious removal effect on lignin. With alkali concentration and the solid liquid ratio increasing, the removal effect also increased. It played a very important role to promote the subsequent enzymatic hydrolysis reaction. At the same time alkali removing hemicellulose was also very obvious. As the temperature and treatment time increasing, main chemical components and sugar content in liquid was changing. But from the point of view of reducing energy consumption, the best dilute alkali (NaOH) pretreatment condition was as follows, solid liquid ratio:1:15, alkali concentration:1.5%, the processing time:80min and temperature:100℃.4. Researching on four aspects of growth temperature, solid liquid ratio, substrate concentration, medium pH, inoculum size to determine the most optimal condition of white-rot fungi p969 to degrade cellulose. According to the results obtained, the effect sequence of various factors was as follows, growth temperature> solid-liquid ratio> substrate concentration> inoculum size> medium pH. The most optimal condition obtained as follows:inoculum size (diameter 5 mm):1 piece/g, solid liquid ratio:1:25, medium pH3.0, temperature:32℃. Under the condition, sugar content in the fermented liquid was 432.33 mg/g.5.Analysing sample crystallinity by FT-IR and XRD, crystallinity of samples treated by dilute acid fell from 56.81% to 54.96%, decreased by 1.91%; After dilute alkali pretreating, its crystallinity fell from 56.81% to 54.84%, decreased by 1.97%; After biological pretreating, the degree of crystallinity declined significantly, from 56.81% to 38.79%, crystallinity decreased by 18.5%. But after dilute alkali treatment, sugar content was 328.82 mg/g in the liqud which was the highest. Effect order of different pretreatment method was as followes:dilute alkali pretreatment> biological pretreatment> dilute acid pretreatment. Through scanning electron microscopy (sem), the effect order of different pretreatment methods was as follows:dilute alkali pretreatment> biological pretreatment> dilute acid pretreatment.Therefore, the effect of dilute alkali pretreatment on Pennisetum sp. cellulose was best. But dilute alkali pretreatment produced large amounts of waste liquid, and cost was higher, samples must be washed to be neutral before enzymolysis, so its prospect of application was limited. Although the effect of biological pretreatment was not good as dilute alkali pretreatment, the cost was lower than the former. Because of smaller pollution, lower energy consumption, it has more bright application prospect.In summary, the best crafts of enzymatic hydrolysis of cellulose for Pennisetum sp.was as follows:Pennisetum sp.â†'dried under 65℃â†'sifted through 20 meshâ†'vaccinated p969 to fermentate, reaction conditions:inoculum size (diameter 5 mm) 1 piece/g, solid liquid ratio 1:25,medium pH 3.0, temperature 32℃.