Bacteria inhabiting artificially inoculated xylem of Picea abies

Bacteria inhabiting the xylem of Norway spruce (Picea abies (L.) H. Karsten) were investigated. The trees had been wounded and artificially inoculated with fungi and bacteria obtained from wounds of naturally infected spruce. One and five growing seasons after inoculation the Gram‐negative bacterial population present in the stem of inoculated trees were analysed.

The Gram‐negative bacteria isolated from the trees were identified on the basis of morphological, biochemical and physiological tests and whole‐cell fatty acid composition. The predominant strains were Enterobacteriaceae fermenter strains (E. agglomerans or E. sakazakii), fluorescent and yellow pigmented Pseudomonas, Acinetobacter and Moraxella spp. All Gram‐positive bacteria were Bacillus species.

The Gram‐negative bacteria of Norway spruce differed from the Gram‐positive species in possessing stronger lipolytic activity and in their ability to utilize pine resins for growth. Gram‐positive bacteria were generally able to utilise cellulose and hemicellulose, whereas among the Gram‐negative bacteria only one xylanolytic (yellow Pseudomonas) strain was found.     

施加内生真菌拟茎点霉（Phomopsis sp.）对茅苍术凋落物降解及土壤降解酶活性的影响

通过向盆栽土壤中分别添加茅苍术(Atractylodes lancea (thunb) DC.)凋落物（CK）、内生真菌拟茎点霉（Phomopsis sp. 编号B3）和灭菌凋落物(MB)、内生真菌和凋落物(WB)、内生真菌和凋落物及菌体发酵液(WBF)、凋落物和灭菌发酵液 (WMF) 后,定期检测凋落物纤维素、木质素降解率,测定土壤纤维素酶和木质素酶活性,并利用巢式PCR方法跟踪土壤中活体内生真菌B3动态变化,研究了土壤施加内生真菌对掉落的茅苍术残体的分解及土壤降解酶活性影响。结果表明,植物内生真菌离开宿主进入土壤仍具有生理活性,能适应非宿主环境,存活30d之久。在此期间,内生真菌在富含凋落物的土壤中明显加快纤维素、木质素的降解,在10d、30d、60d取样测定,处理组中WBF和MB的土壤纤维素酶活性显著高于其他处理组,处理组MB和WB的土壤木质素酶活性显著高于其他处理组。     

羟丙基甲基纤维素高吸水性树脂制备与性能表征

以羟丙基甲基纤维素为骨架材料,丙烯酸为接枝共聚单体,过硫酸铵-亚硫酸氢钠为引发剂,聚乙二醇200二丙烯酸酯为交联剂,在微波辐射的条件下通过接枝聚合反应制备高吸水性树脂,并对高吸水性树脂的吸液倍率、吸液速率、保水性能以及红外光谱、热稳定性、表观形态进行表征。结果表明,羟丙基甲基纤维素与丙烯酸质量比为1/7、中和度为65%、引发剂与丙烯酸质量分数为1%、交联剂与丙烯酸质量分数为0. 4%、反应时间为4. 5 min是较优的制备方法,该条件下制备的羟丙基甲基纤维素高吸水性树脂吸水倍率可达497. 13 g/g,吸盐倍率为61. 70 g/g;35℃条件下,该高吸水性树脂可保水48 h以上;重复使用6次后,该高吸水性树脂仍具有较高的吸液倍率。     

玉米秸秆纤维素的磷酸结合碱性过氧化氢分离

传统玉米秸秆纤维素分离工艺中,一般采用硫酸等强酸进行处理,存在酸腐蚀性强及碱消耗量大等问题。基于此,研究以磷酸预处理结合碱性过氧化氢的处理工艺,探究处理过程中玉米秸秆纤维素、半纤维素及木质素质量分数的变化。通过单因素试验优化得到适宜工艺为:磷酸处理温度150℃,处理时间1. 5 h,磷酸质量分数1. 67%,氢氧化钠质量分数1. 0%,过氧化氢质量分数2. 0%,处理温度50℃,处理时间3 h,在此条件下制备的玉米秸秆纤维素得率达89. 02%,半纤维素去除率达93. 25%,木质素去除率达95. 18%,纤维素质量分数达90. 19%,同时在稀磷酸处理过程获得的滤液中能得到高副加值产物木糖、阿拉伯糖以及糠醛,半纤维素的回收率高达93. 81%。通过FTIR、SEM、AFM和XRD等测试分析发现,玉米秸秆经过磷酸处理后能有效去除半纤维素,碱性过氧化氢处理能脱除木质素组分,两步处理过程中秸秆纤维素晶型无变化,但是结晶度显著提高,热稳定性增强。     

NaOH协同辐照预处理提高稻草纤维素酶解转化率

为降低预处理成本,提升稻草纤维素的酶解效果,采用NaOH协同⁶⁰Co-γ射线辐照处理稻草,研究其对稻草中纤维素酶解转化率的影响,利用扫描电镜(SEM)、红外光谱(FT-IR)分析协同预处理对稻草微观结构的影响,并通过正交试验对协同预处理条件参数进行优化。结果表明,NaOH协同辐照预处理能显著提高稻草纤维素酶解转化率,优化后的预处理条件为400 kGy辐照剂量的稻草结合2%NaOH溶液,固液比1:15,50℃条件下处理4 h,按照10 FPU·g^-1加入纤维素酶溶液,于50℃、130 r·min^-1条件下气浴恒温振荡,酶解24 h后,其稻草纤维素转化率达到78.54%±1.20%。本研究结果为农业废弃物资源能源化高效利用提供了技术支撑和理论依据。     

ATRP法制备纤维素-油脂-糠醛热塑性弹性体及性能表征

通过"从主链接枝"原子转移自由基聚合(ATRP)法,采用分步聚合策略,成功制备了一种乙基纤维素接枝嵌段共聚物乙基纤维素-g-甲基丙烯酸月桂酯-b-甲基丙烯酸四氢糠基酯(EC-g-P(LMA-b-THFMA))。对聚合物的热力学性能研究发现:共聚物中存在两个热转变,分别发生在-35℃和49～56℃时,表明该共聚物存在微相分离;机械性能分析表明该共聚物具有优异的热塑性弹性体行为,伸长率为89%～147%,拉伸强度为1.7～9.5 MPa。循环拉伸机械性能研究表明EC-g-P(LMA-b-THFMA200)的弹性恢复系数高达92%以上。乙基纤维素接枝共聚物的机械性能具有明显的增强作用,较线性聚合物P(LMA-b-THFMA)的机械强度提高了1.36倍。     

玉米秸秆稀酸水解糖化法影响因子的研究

该文通过分析水解还原糖成分,研究了温度、时间、稀酸浓度、固形物含量对水解效率的影响;并结合残渣组分分析研究了稀酸水解过程中纤维素、半纤维素降解的规律.研究表明:在试验条件下玉米秸秆的水解主要以半纤维素为主,随着温度、稀酸浓度和水解时间的增加,纤维素的水解逐渐增强.当水解温度超过1000C后,水解得糖率迅速增加,超过110℃,纤维素开始水解;玉米秸秆的水解在前40 min就基本完成,过长的水解时间对水解效率的提高意义不大;水解的酸浓度应控制在1.5%左右;玉米秸秆在低固含物的条件下,水解效率相对较高.方差分析结果显示:温度、酸浓度对水解效率的影响最大,温度和固含物的影响次之,粒径的影响不显著;温度和酸浓度、温度和时间的交互作用对试验结果有影响显著.根据方差分析,最佳水解条件A3B2C3D1E1:温度125℃、时间80 min、稀酸浓度1.5%、固形物含量7.5%,在该条件下水解还原糖得率为32.71%.     

纤维素酶水解棕榈壳制取乙醇研究

先将棕榈壳置于多功能水解反应器中于200℃,4.0 MPa,液固比15∶1,搅拌转速500 r/min条件下纯水预处理5 min,半纤维素和纤维素含量分别从21.74%,45.42%变为2.35%,47.63%,再以一定比例混合预处理液与棕榈壳残渣,研究液固比,温度,加酶量和时间对棕榈壳糖化工艺的影响,结果表明液固比为16∶1最合适,低温37℃比高温50℃更有利于棕榈壳的糖化,从长时间看,加酶量并不完全与原料转化率成正相关,以小于10 FPU/g为宜。糖化效果取决于β-葡萄糖苷酶对葡萄糖的耐受性以及预处理效果。采用酿酒酵母对糖化液发酵,乙醇得率为77%。通过电镜扫描发现,预处理与酶解后的残渣的结构比原料明显疏松,长条状晶束结构有着不同的程度的破坏,但木质素结构破坏较小。     

大豆油不同添加水平对瘤胃体外发酵和产气的影响

本试验通过体外培养,研究在精粗比为30:70(偏粗型)日粮类型条件下,不同大豆油添加水平对产气量、甲烷产量、pH值和纤维降解率的影响.结果表明:随着大豆油添加水平的提高,产气量和甲烷产量逐渐降低,且各添加组显著低于对照组;pH值随着培养时间的延长,各添加水平在不同培养时间点与对照组相比均上升,其中添加量为4%和6%与对照组相比差异显著(P<0.05),添加量为8%时,与对照组相比差异极显著(P<0.01);培养24 h后.纤维降解率的抑制潜力8%水平最大,与对照组相比差异极显著(P<0.01),其次是6%的添加水平.与对照组相比差异显著(P<0.05).而2%和4%添加水平对纤维降解率的抑制程度与对照组相比差异不显著(P>0.05).通过产气量、pH值和纤维降解率综合考察大豆油对瘤胃体外发酵和产气的影响,本试验得出大豆油的最适添加量为4%.     

Microbial protein formation of different carbohydrates in vitro

The aim of this study was to investigate the microbial protein yield of different pure carbohydrates to contribute to a more precise prediction of the microbial protein formed in the rumen. In a first experiment, sucrose, wheat starch, microcrystalline cellulose and citrus pectin were incubated for 8 and 24 hr in the modified Hohenheim gas test (HGT) system (3 runs × 2 syringes) including gas production, ammonia and short‐chain fatty acid concentration measurements. Ammonia values were used for estimation of the microbial protein formation. In a second experiment, the same substrates were incubated for 96 hr in the HGT system (2 runs × 3 syringes) and gas production was measured after 2, 4, 6, 8, 12, 16, 24, 30, 36, 48, 60, 72 and 96 hr of incubation to obtain the fermentation kinetics and the time of half‐maximal gas production (t_1/2) of the substrates. The substrates differed considerably in their fermentation kinetics, and therefore, comparison on the basis of t_1/2 was chosen as the most meaningful. At t_1/2, microbial protein yield [g/kg dry matter] was higher for cellulose than for sucrose and pectin and higher for starch than for sucrose. The microbial protein expressed in g/L gas production was higher for starch and cellulose than for sucrose and pectin at t_1/2. Effects of carbohydrates related to ruminal pH may remain undetected in in vitro trials.