酸性蛋白酶预处理对小麦秸秆纤维素酶酶解的影响

为提高小麦作物秸秆酶解效率,对小麦秸秆进行酸性蛋白酶酶解预处理,然后进行纤维素酶酶解。以最终得糖率为指标考察酸性蛋白酶预处理对纤维素酶降解小麦秸秆的影响。采用单因素和正交实验对酸性蛋白酶酶解预处理条件进行优化,结果表明预处理小麦秸秆最优条件为:反应温度45℃,反应时间4h,加酶量0.5%(酶∶原料),固液比1∶12(g/mL),pH为3。经预处理条件优化后,纤维素酶解率达73.12%。     

牛血清蛋白对纤维素酶水解小麦秸秆的影响

在以分别被稀硫酸和氢氧化钠处理的小麦秸秆为底物进行纤维素酶解时添加牛血清蛋白（BSA）来评估BSA对酶解的影响,当接入纤维素酶40Ug秸秆,添加牛血清蛋白0.04g时,反应48h,还原糖得率分别提高30%和22%,添加牛血清蛋白后酸处理的秸秆水解速率更快,酶解液中酶失活趋势减小,以滤纸为底物测定纤维素酶活力时添加牛血清蛋白能将酶活提高1倍以上,从而推断牛血清蛋白可以提高纤维素酶的稳定性并减少酶因吸附木质素而失活,提高酶的水解效率。     

Effect of ammonia fiber expansion on the available energy content of wheat straw fed to lactating cattle and buffalo in India

The seasonal lack of availability of lush green forages can force dairy farmers in developing nations to rely on crop residues such as wheat and rice straw as the major feed source. We tested whether ammonia fiber expansion (AFEX) treatment of wheat straw would increase the energy available to Murrah buffalo and Karan-Fries cattle consuming 70% of their diet as wheat straw in India. Forty lactating animals of each species were blocked by parity and days in milk and randomly assigned to 1 of 4 treatment diets (n = 10). Treatments were a nutrient-rich diet with 0 to 20% straw (positive control; PC) and 3 high-straw diets with various levels of AFEX-treatment: (1) 70% untreated straw (no AFEX), (2) 40 to 45% untreated straw with 25 to 30% AFEX-treated straw (low AFEX), and (3) 20% untreated straw with 50% AFEX-treated straw (high AFEX). The AFEX-treated straw was pelleted. Urea was added to the no and low AFEX diets so they were isonitrogenous with the high AFEX diet. Animals were individually fed the PC diet for 14 d followed by 7 d of adaptation to treatments, full treatments for 28 to 35 d, and finally PC diets for 21 d. Compared with buffalo fed the PC diet, those fed high-straw diets consumed 29% less feed dry matter, put out 16% less milk energy, and lost 0.8 kg/d more body weight; the AFEX treatment of straw did not alter intake or milk production but greatly ameliorated the body weight loss (?1.0 kg/d for no AFEX and ?0.07 kg/d for high AFEX). In Karan-Fries cattle, high-straw diets decreased dry matter intake by 39% and milk energy by 24%, and the high AFEX diet increased intake by 42% and milk energy by 18%. The AFEX treatment increased digestibilities of organic matter, dry matter, neutral detergent fiber, acid detergent fiber, and crude protein by 6 to 13 percentage points in buffalo and 5 to 10 points in cattle. In conclusion, AFEX treatment increased the digestibility and energy availability of wheat straw for lactating buffalo and cattle and has commercial potential to improve milk production and feed efficiency when high-quality forages or grains are not available.     

酶法水解麦胚蛋白的研究

研究了利用As1398蛋白酶水解小麦胚芽蛋白的条件,正交实验结果表明:温度为48℃、底物固形物的质量分数为9%、酶用量为3000U/g、时间为4.5h的条件下,小麦胚芽水解蛋白的得率最高。     

Prediction of ammonia emission from dairy cattle manure based on milk urea nitrogen: Relation of milk urea nitrogen to ammonia emissions

The main objectives of this study were to assess the relationship between ammonia emissions from dairy cattle manure and milk urea N (MUN; mg/dL) and to test whether the relationship was affected by stage of lactation and the dietary crude protein (CP) concentration. Twelve lactating multiparous Holstein cows were randomly selected and blocked into 3 groups of 4 cows intended to represent early [123 ± 26 d in milk (DIM)], mid (175 ± 3 DIM), and late (221 ± 12 DIM) lactation stages. Cows within each stage of lactation were randomly assigned to a treatment sequence within a split-plot Latin square design balanced for carryover effects. Stage of lactation formed the main plots (squares) and dietary CP levels (15, 17, 19, and 21% of diet dry matter) formed the subplots. The experimental periods lasted 7 d, with d 1 to 6 used for adjustment to diets and d 7 used for total collection of feces and urine as well as milk sample collection. The feces and urine from each cow were mixed in the proportions in which they were excreted to make slurry that was used to measure ammonia emissions at 22.5°C over 24 h using flux chambers. Samples of manure slurry were taken before and after ammonia emission measurements. The amount of slurry increased by 22% as dietary CP concentration increased from 15 to 21%, largely because of a greater urine volume (25.3 to 37.1 kg/d). Initial urea N concentration increased linearly with dietary CP from 153.5 to 465.2 mg/dL in manure slurries from cows fed 15 to 21% CP diets. Despite the large initial differences, the final concentration of urea N in manure slurries was less than 10.86 mg/dL for all dietary treatments. The final total ammoniacal N concentration in manure slurries increased linearly from 228.2 to 508.7 mg/dL as dietary CP content increased from 15 to 21%. Ammonia emissions from manure slurries ranged between 57 and 149 g of N/d per cow and increased linearly with dietary CP content, but were unaffected by stage of lactation. Ammonia emission expressed as a proportion of N intake increased with percentage CP in the diet from about 12 to 20%, whereas ammonia emission as a proportion of urinary urea N excretion decreased from 67 to 47%. There was a strong relationship between ammonia emission and MUN [ammonia emission (g/d per cow) = 25.0 (±6.72) + 5.03 (±0.373) × MUN (mg/dL); R² = 0.85], which was not different among lactation stages. Milk urea N concentration is one of several factors that allows prediction of ammonia emissions from dairy cattle manure.     

小麦面筋蛋白酶法改性研究

本研究采用中性蛋白酶水解小麦面筋蛋白,就几种因素对水解程度的影响、酶解条件及酶解物的功能性质进行了系统研究,并分析了酶解前后巯基含量的变化,酶解后的小麦面筋蛋白功能性质显著提高。     

Structural changes in wheat straw components during decay by lignin-degrading white-rot fungi in relation to improvement of digestibility for ruminants

Structural changes and resulting in-vitro dry matter digestibility (IVDMD) were determined during the course of solid-state fermentation of wheat straw using the lignin-degrading white-rot fungi Sporotrichum pulverulentum, Pycnoporus cinnabarinus and Cyathus stercoreus. The first fungus grew very rapidly on straw but degraded hemicelluloses and cellulose non-selectively resulting in very low IVDMD increases (50% after 35% weight loss). P. cinnabarinus and C. stercoreus preferentially degraded hemicelluloses achieving high improvements in IVDMD (maximum increase of 63 and 94%, respectively) with limited dry weight losses (12 and 18% after 7 and 13 days, respectively). The three fungi exhibited some selectivity among the individual hemicellulose components: O-acetyls were removed essentially at the same rate as xylan, while uronic acids accumulated as incubation proceeded. Conversely, the arabinose content decreased rapidly, especially with C. stercoreus and P. cinnabarinus, suggesting that removal of this pentose was partly responsible for digestibility improvement. Esterified phenolic acids were rapidly degraded during the first stages of decay by all three fungi although P. cinnabarinus and C. stercoreus degraded ferulic acid faster than p-coumaric acid. Lignin was preferentially degraded compared to polysaccharides by all three fungi. The amount of lignin removed, as determined by Klason, correlated well with IVDMD improvement (r=?0.97), while acid detergent lignin (ADL) showed a lower correlation (r=-0.86). Acidolysis yields of decayed lignin pointed to preferential degradation of β-O-4 ether linked units by the fungi. Syringyl units were removed faster than guaiacyl units only after 5 to 10% weight loss was obtained.     

Structural convergence of maize and wheat straw during two-year decomposition under different climate conditions

Straw decomposition plays an important role in soil carbon sequestration. Litter quality and climate condition are considered to be key factors that regulate straw decomposition. This study investigated the decomposition characteristics of wheat and maize straw under cold temperate, warm temperate, and midsubtropic climate conditions, and examined whether the chemical structures of straw residues became similar during decomposition under different climate conditions. Straws were put in 0.074-mm-mesh size litter bags to exclude soil fauna and buried in black soil plots at three experimental stations located in the aforementioned climate regions to rule out the impact of soil type. The decomposition rate constants of wheat straw and maize straw increased linearly with temperature, and the former was more sensitive to temperature. Climate conditions and straw quality had marked effects on the residual material structure in the first half year of decomposition, but then decreased. Wheat and maize straw showed common decomposition characteristics with a decrease of O/N-alkyl carbons and di-O-alkyls, and a simultaneous increase of alkyl carbons, aromatic carbons, aromatic C-O groups, and COO/N-C ═ O groups. Overall, the results indicated that the chemical compositions of the two types of straw became similar after 2-year decomposition under different climate conditions.     

小麦胚酶解生产高营养天然麦胚饮料

探讨了利用一种全新的蛋白酶-Flavourzyme水解小麦胚的工艺,以生产高营养天然麦胚饮料。通过正交实验确定了最佳的水解工艺参数:温度55℃,pH7.0,料水比1∶8～1∶10,Flavourzyme的使用量为40LAPU/g蛋白质,此工艺能使小麦胚的总固形物和蛋白质的提取率分别达到60.3%和70.4%。     

麦草浆氧脱木素过程中甲醇生成的经验模型

研究了麦草浆氧脱木素过程甲醇的生成规律。结果表明用碱量、氧压、保温时间、反应温度或者它们的数学转变形式对甲醇生成量呈直线关系,据此建立了甲醇生成的经验模型CMethanol=α·（AA）~（1/2）·（Tm-）·（PO2）n·Log（0.2547t＋1）。验证发现,该模型能很好地预测氧脱木素过程中甲醇的生成规律（R2=0.977）。这将为降低麦草浆氧脱木素过程甲醇的生成量提供参考。     

胃蛋白酶水解小麦蛋白工艺的研究

以小麦蛋白为原料,采用胃蛋白酶对其水解工艺进行优化。以水解度、小麦肽的得率为响应值,设计了四因素三水平的中心组合响应面试验。通过优化组合得到最佳水解条件为温度37℃、pH2、底物浓度1%和加酶量1500U/g,此时水解度为7.8%,小麦肽的得率为55.95%。     

Production of lactic acid from xylose and wheat straw by Rhizopus oryzae

Rhizopus oryzae NBRC 5378 was the best among 56 strains of R. oryzae for the production of lactic acid from xylose. This strain produced lactic acid from wheat straw powder by a simultaneous saccharification and fermentation process, with a yield of 0.23 g/g from cellulose and hemicellulose in wheat straw.     

麦草浆的生物漂白与酶法改性

用木聚糖酶处理未漂麦草浆,纸浆的可漂性得到改善,用氯量减少工纸浆白度提高,用纤维素酶和半纤维素酶处理漂白麦草浆可明显改善纸浆的性能,如滤水性、脆性、强度和白度等,工业化试验表明,草浆的生物漂白与酶法改性具有较好的环境效益和经济效益。     

利用纤维素酶降解稻草粉的研究

纤维素是自然界中存在最广泛的一类碳水化合物,同时它也是地球上数量最大的再生资源.目前,自然界中纤维素只有一小部分得到了利用,绝大多数纤维素不仅被白白浪费,而且还会造成环境污染.利用微生物生产的纤维素酶将其转化为人类急需的能源、食物和化工原料,对于人类社会解决环境污染、食物短缺和能源危机具有重大的现实意义.纤维素的酶解是一个复杂的生化过程,其作用机制的研究一直受到人们的重视,许多学者提出了各种假说.目前较为普遍接受的理论主要有三个:协同理论、原初反应理论和碎片理论.本文利用单因子实验得到了稻草粉酶解糖化的最佳条件:稻草粉先经1.0%NaOH+1.0%H2O2预处理,底物浓度为2.5%,糖化温度50℃,反应体系pH4.8,滤纸酶:β-葡萄糖苷酶＝1 :1.     

Stimulation of microbial urea hydrolysis in groundwater to enhance calcite precipitation

Addition of molasses and urea was tested as a means of stimulating microbial urea hydrolysis in the Eastern Snake River Plain Aquifer in Idaho. Ureolysis is an integral component of a novel remediation approach for divalent trace metal and radionuclide contaminants in groundwater and associated geomedia, where the contaminants are immobilized by coprecipitation in calcite. Generation of carbonate alkalinity from ureolysis promotes calcite precipitation. In calcite-saturated aquifers, this represents a potential long-term contaminant sequestration mechanism. In a single-well experiment, dilute molasses was injected three times over two weeks to promote overall microbial growth, followed by one urea injection. With molasses addition, total cell numbers in the groundwater increased 1-2 orders of magnitude. Estimated ureolysis rates in recovered groundwater samples increased from < 0.1 to > 25 nmol L(-1) hr(-1). A quantitative PCR assay for the bacterial ureC gene indicated that urease gene numbers increased up to 170 times above pre-injection levels. Following urea injection, calcite precipitates were recovered. Estimated values for an in situ first order ureolysis rate constant ranged from 0.016 to 0.057 d(-1). Although collateral impacts such as reduced permeability were observed, overall results indicated the viability of manipulating biogeochemical processes to promote contaminant sequestration.     

酶法降解小麦秸秆碱预处理浓度的选择及酶解产物的检测

通过研究氢氧化钠溶液预处理小麦秸秆浓度与β-葡聚糖酶对预处理后的小麦秸秆降解产物的关系,确定酶解小麦秸秆的最佳碱处理浓度,分析降解产物主要成分.将不同浓度碱处理的小麦秸秆用72％硫酸溶液酸解,高效液相色谱法(HPLC)测定酸降解产物中的葡萄糖及木糖含量,并进而推算出小麦秸秆中的纤维素及半纤维素含量,由纤维素、半纤维素含量及酶解转化率决定最佳碱处理条件;HPLC定性检测β-葡聚糖酶降解预处理后的小麦秸秆的主要降解产物 .结果表明,NaOH预处理小麦秸秆的最佳浓度为1％,处理后的小麦秸秆纤维素、半纤维素含量分别为44.13％、21.34％;β-葡聚糖酶降解小麦秸秆的主要产物为纤维二糖. 本研究为以小麦秸秆为原料酶解制备纤维寡糖提供了依据.     

Protamex复合蛋白酶酶解猪骨动力学模型的建立

研究采用均匀实验优化了Protamex复合蛋白酶酶解猪骨的工艺,并利用SPSS软件对酶解过程进行数学模拟,得到了Protamex复合蛋白酶酶解猪骨的动力学模型,同时测定了米氏常数Km与最大反应速率Vmax。结果表明,酶解时间5.7h,酶解温度45℃,pH为7.6,加酶量0.49%,料液比为1:22.7时,水解度最大为10.21%;酶解动力学方程为Y=1.918lnx-0.779,符合对数方程;Km=221.27mmol/L,Vmax=0.1448mmol/L·min。     

复合酶法制备小麦低聚肽的工艺研究

以小麦蛋白为原料,采用酶解法水解小麦蛋白制备小麦低聚肽。筛选出水解度最佳的单酶以及复合酶。通过单因素试验以及正交试验优化小麦蛋白的水解工艺的条件可以得出:胰蛋白酶与碱性蛋白酶复合水解时,小麦蛋白的水解度最高,水解度可达到37.72%。最佳条件为:先采用胰蛋白酶进行水解,水解温度40℃、p H为10、酶添加量7%、水解时间4 h;再利用碱性蛋白酶水解小麦蛋白,水解温度65℃、p H为8、酶添加量7%、水解时间3 h。采用高效液相色谱测出水解产物分子量大部分集中在1374~445 Da,且由峰面积计算含量为52.03%。     

Cell wall porosity and available surface area of wheat straw and wheat grain fractions

Interactions between polymers define many of the physical properties of plant cell walls. The most important of these are available surface area and the related measures of pore size and distribution. Gas adsorption and mercury porosimetry methods for the measurement of these parameters in wheat straw, whole wheat grain and grain fractions were compared. All of the samples examined had a very low surface area regardless of the means of measurement. However mercury porosimetry gave values 10-fold greater than gas adsorption. It is suggested that the assumptions made about pore structure necessary for the use of mercury porosimetry do not hold for plant material and that closed pore systems were distorted by the very high pressures involved. Gas adsorption gave a more realistic assessment of 2–8 m² g⁻¹ with grain having a lower available surface than vegetative walls. Pore regimes in both grain and straw were very similar and were determined in grain by the bran fraction. Little structure could be found associated with the starchy endosperm. Pores with radii of 1·5–3 nm predominated in wheat cell walls. These are below the size which would allow free penetration of the wall by degrading enzymes. ©1997 SCI