甘蔗渣纤维素降解菌株的筛选与鉴定

甘蔗渣是制糖工业的主要副产物。筛选甘蔗渣纤维素降解菌株对甘蔗渣乙醇产业具有重要的意义。以甘蔗渣为原料,通过分离和纯化得到14株菌株,对其进行纤维素刚果红平板染色实验和滤纸崩解实验,最终获得3株可以生产纤维素酶的菌株02-2-2、21-1-2和40-1-1。酶活性测定结果表明,菌株40-1-1的酶活力在培养3 d后达到最高,为27.26 U/mg。通过形态学和分子生物学鉴定,菌株02-2-2为枝顶孢属(Acremonium sp.),菌株21-1-2和40-1-1为光滑短梗霉属(Acrophialophora sp.)。研究筛选的菌株将为开展甘蔗渣纤维素降解利用提供参考。     

Enhanced xylanase and endoglucanase production from Beauveria bassiana SAN01, an entomopathogenic fungal endophyte

This study was undertaken to explore alternative applications of the widely known entomopathogenic/endophytic fungus, Beauveria bassiana, besides its sole use as a biocontrol agent. B. bassiana SAN01, was investigated for the production of two glycoside hydrolases, xylanase and endoglucanase under submerged conditions. Among the different biomass tested, wheat bran provided the best results for both xylanase and endoglucanase, and their production levels were further enhanced using response surface methodology. Under optimised conditions, heightened yields of 1061 U/ml and 23.03 U/ml were observed for xylanase and endoglucanase, respectively, which were 3.44 and 1.35 folds higher than their initial yields. These are the highest ever production levels reported for xylanase and endoglucanase from any B. bassiana strain or any known entomopathogenic fungi. Furthermore, the efficacy of xylanase/endoglucanase cocktail in the saccharification of sugarcane bagasse was evaluated. The highest amount of reducing sugar released from the pretreated biomass by the action of the crude Beauveria enzyme cocktail was recorded at 30°C after 8 h incubation. The significant activities of the hydrolytic enzymes recorded with B. bassiana in this study thus present promising avenues for the use of the entomopathogen as a new source of industrial enzymes and by extension, other biotechnological applications.     

Enhancement of the enzymatic digestibility of sugarcane bagasse by steam pretreatment impregnated with hydrogen peroxide

Sugarcane bagasse was subjected to steam pretreatment impregnated with hydrogen peroxide. Analyses were performed using 2³ factorial designs and enzymatic hydrolysis was performed at two different solid concentrations and with washed and unwashed material to evaluate the importance of this step for obtaining high cellulose conversion. Similar cellulose conversion were obtained at different conditions of pretreatment and hydrolysis. When the cellulose was hydrolyzed using the pretreated material in the most severe conditions of the experimental design (210°C, 15 min and 1.0% hydrogen peroxide), and using 2% (w/w) water‐insoluble solids (WIS), and 15 FPU/g WIS, the cellulose conversion was 86.9%. In contrast, at a milder pretreatment condition (190°C, 15 min and 0.2% hydrogen peroxide) and industrially more realistic conditions of hydrolysis (10% WIS and 10 FPU/g WIS), the cellulose conversion reached 82.2%. The step of washing the pretreated material was very important to obtain high concentrations of fermentable sugars. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012     

Enzymatic saccharification of sugar cane bagasse by continuous xylanase and cellulase production from cellulomonas flavigena PR‐22

Cellulase (CMCase) and xylanase enzyme production and saccharification of sugar cane bagasse were coupled into two stages and named enzyme production and sugar cane bagasse saccharification. The performance of Cellulomonas flavigena (Cf) PR‐22 cultured in a bubble column reactor (BCR) was compared to that in a stirred tank reactor (STR). Cells cultured in the BCR presented higher yields and productivity of both CMCase and xylanase activities than those grown in the STR configuration. A continuous culture with Cf PR‐22 was run in the BCR using 1% alkali‐pretreated sugar cane bagasse and mineral media, at dilution rates ranging from 0.04 to 0.22 1/h. The highest enzymatic productivity values were found at 0.08 1/h with 1846.4 ± 126.4 and 101.6 ± 5.6 U/L·h for xylanase and CMCase, respectively. Effluent from the BCR in steady state was transferred to an enzymatic reactor operated in fed‐batch mode with an initial load of 75 g of pretreated sugar cane bagasse; saccharification was then performed in an STR at 55°C and 300 rpm for 90 h. The constant addition of fresh enzyme as well as the increase in time of contact with the substrate increased the total soluble sugar concentration 83% compared to the value obtained in a batch enzymatic reactor. This advantageous strategy may be used for industrial enzyme pretreatment and saccharification of lignocellulosic wastes to be used in bioethanol and chemicals production from lignocellulose. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:321–326, 2016     

Homogeneous modification of sugarcane bagasse cellulose with succinic anhydride using a ionic liquid as reaction medium

The homogeneous chemical modification of sugarcane bagasse cellulose with succinic anhydride using 1-allyl-3-methylimidazolium chloride (AmimCl) ionic liquid as a reaction medium was studied. Parameters investigated included the molar ratio of succinic anhydride/anhydroglucose units in cellulose in a range from 2:1 to 14:1, reaction time (from 30 to 160min), and reaction temperature (between 60 and 110 degrees C). The succinylated cellulosic derivatives were prepared with a low degree of substitution (DS) ranging from 0.071 to 0.22. The results showed that the increase of reaction temperature, molar ratio of SA/AGU in cellulose, and reaction time led to an increase in DS of cellulose samples. The products were characterized by FT-IR and solid-state CP/MAS (13)C NMR spectroscopy, and thermal analysis. It was found that the crystallinity of the cellulose was completely disrupted in the ionic liquid system under the conditions given. The data also demonstrated that homogeneous modification of cellulose with succinic anhydride in AmimCl resulted in the production of cellulosic monoester. The thermal stability of the succinylated cellulose decreased upon chemical modification.     

Synthesis and properties of polyaniline–cellulose acetate blends: The use of sugarcane bagasse waste and the effect of the substitution degree

Membranes of blends of polyaniline (PANi) and cellulose acetate (CA) produced from sugarcane bagasse with different degrees of substitution were produced and characterized using various techniques. Results showed that incorporation of PANi into the CA matrices leads to significant alterations of the blend morphologies, with phase separation, and that these differences are less significant for PANi/cellulose triacetate blends. The blends also showed a significant increase in electrical conductivity, with that of PANi/cellulose diacetate demonstrating an almost 200-fold increase.     

直接加热膨化蔗渣酶法水解的研究

采用加热时间为２０ｍｉｎ,压力为２．０ＭＰａ,温度为１２０℃的直接加热膨化甘蔗渣为水解底物、日本ｙｓｋｕｌｔ生物化学试剂公司生产的ｏｎｏｚｕｋＲＳ型纤维纯洁酶粉进行蔗渣的酶法水解实验,考察了蔗渣中纤维素的酶解还原糖得率与反应时间、酶浓度、ｐＨ值、缓冲液种类、离子强度以及固液比的关系,结果表明：当固液比为５％（ｗ／ｖ）,酶浓度＞１．２０ｍｇ／ｍｌ时,还原糖得率随酶浓度的增加变化不显著;本实验条件下,缓冲液种类和离子强度对还原糖得率几乎没有影响;水解最适宜ｐＨ值为４．２～４．９;最佳反应温度为５０℃。     

蔗渣催化氧化一步法制草酸

本报告讨论了蔗渣催化氧化一步法直接制草酸工艺,在最佳反应条件下蔗渣制草酸收率在80％左右,草酸纯度可达99.4％,硝酸回收率可达90％。此法也可用于其它废纤维植物,例如谷壳、稻草和玉米杆等生产草酸。     

用普通纯水代替缓冲液时蔗渣酶法水解反应的考察

使用Onozuk RS型纤维素酶,以普通的城市自来水和纯水代替缓冲液,直接加热膨化甘蔗渣进行酶法水解实验研究,结果表明:所使用的各种水代替缓冲液时,蔗渣酶解还原糖得率基本不变,还原糖得率最高时的最适宜pH为4.2～4.9,当蔗渣浓度大于1％时,反应液的pH恰好处于最适宜pH范围内,还原糖得率最高的酶解反应温度为50℃。     

蔗渣水解液发酵乙醇的研究

研究了酵母（Ｐｉｃｈｉａｓｔｉｐｉｔｉｓ）Ｙ７１２４在限制供氧条件下尽管反应初期葡萄糖消耗速率大于木糖,但在一定时间后,葡萄糖的消耗速率变慢,而木糖消耗速率变快直至耗尽的现象。建立了气升柱以Ｐ．Ｓｔｉｐｉｔｉｓ转化木糖为目的和以溢流柱Ｓａｃｈａｒｏｍｙｃｅｓｃｅｒｉｖｉｓｉａｅ转化残留葡萄糖为目的的串联发酵乙醇工艺,即流加５倍浓缩的蔗渣水解液,Ｄ＝０.１ｈ^－１,还原糖总利用率为９７.２％,酒精浓度为４６.５ｇ／Ｌ,生产率为４.１ｇ／Ｌ·ｈ。