大田环境下转Bt基因玉米对土壤酶活性的影响

在大田自然条件下,比较研究了转Bt基因玉米和非转基因亲本玉米在种植和秸秆分解时对土壤酶活性影响的差异。结果表明,与亲本非转基因玉米相比,在各生育期内种植转Bt玉米对土壤蛋白酶和土壤脲酶活性均没有显著影响;在喇叭口期和抽雄期,土壤蔗糖酶和土壤酸性磷酸酶活性显著提高。在秸秆还田后,两种玉米秸秆对土壤酸性磷酸酶活性的影响没有显著差异,但使用转Bt玉米秸秆的土壤蔗糖酶、土壤脲酶和土壤蛋白酶的活性则有显著提高。与亲本玉米相比,在所有观测期内,种植Bt玉米及秸秆还田对土壤酶活性的影响,在影响的幅度及趋势上随玉米生育期和土壤酶种类的不同而产生差异,但没有观测到显著不利影响;商业化Bt玉米的环境释放仍有待长期定位观测和评价。     

Biodelignification of wheat straw and its effect on in vitro digestibility and antioxidant properties

A variety of methods for feed development have been introduced during last few years. Bioprocessed agricultural residues may prove a better alternative to provide animal feed. For the purpose, some white rot fungi were allowed to degrade wheat straw up to 30 days under solid state conditions. Several parameters including loss in total organic matter, ligninolysis, in vitro digestibility of wheat straw and estimation of different antioxidant activities were studied. All the fungi were able to degrade lignin and enhance the in vitro digestibility. Among all the tested fungi, Phlebia brevispora degraded maximum lignin (30.6%) and enhanced the digestibility from 172 to 287 g/kg. Different antioxidant properties of fungal degraded wheat straw were higher as compared to the uninoculated control straw. Phlebia floridensis found to be more efficient organism in terms of higher antioxidant activity (70.8%) and total phenolic content (9.8 mg/ml). Thus, bioprocessing of the wheat straw with the help of these organisms seems to be a better approach for providing the animal feed in terms of enhanced digestibility, higher protein content, higher antioxidant activity and availability of biomass.     

白腐菌胞外提取液与纤维素酶对玉米秸秆的协同酶解研究

通过评价几株白腐菌固体发酵不同时间的胞外提取液与纤维素酶同时加入对玉米秸秆酶解产糖的影响,得到一个较高糖化效果的胞外降解体系,并对其相关影响因素进行研究,进而初探其协同酶解的机制.结果表明,Echinodontium taxodii 2538固体培养5 d的胞外提取液与纤维素酶形成的胞外降解体系的协同酶解效果较好,酸处...     

广谱抗真菌转基因水稻植株化学成分与结构动态变化

【背景】种植广谱抗真菌水稻可能会带来一定的环境生物安全问题,对其植株的化学成分进行实质等同性分析是转基因水稻安全性评价的重要内容之一。【方法】以表达广谱抗真菌蛋白转基因水稻转品1和转品8及其相应非转基因水稻七丝软粘的秸秆为研究材料,采用化学法和扫描电镜技术分析外源基因的导入对水稻秸秆化学成分以及组织显微结构的影响。【结果】（1）在整个生长发育过程中,广谱抗真菌转基因水稻转品1和转品8与其非转基因水稻七丝软粘叶片、叶鞘和茎的纤维素、半纤维素、木质素以及粗蛋白含量的变化趋势基本一致,且品种间化学成分的含量不存在显著差异。（2）广谱抗真菌转基因水稻叶片表皮的硅质瘤状结构以及气孔的形状和致密程度与其非转基因水稻七丝软粘相似;茎壁、厚壁组织、薄壁组织以及大小维管束的形态和分布情况未发生明显变化。【结论与意义】表达广谱抗真菌蛋白转基因水稻秸秆的化学成分和组织显微结构与非转基因水稻基本一致。这为广谱抗真菌转基因水稻的环境安全性评估提供了依据。     

不同年限免耕秸秆覆盖对土壤活性有机碳和碳库管理指数的影响

为探明渭北旱塬免耕秸秆覆盖对春玉米田土壤活性有机碳(LOC)、碳库管理指数(CMI)和作物产量的影响,进而明确该区免耕覆盖的适宜年限,于2001-2010年在陕西合阳县旱农试验站,设置了不同年限处理:1年(S1)、3年(S3)、5年(S5)、8年(S8)和10年(S10)的免耕秸秆覆盖定位试验,以常规耕作(CK)和10年免耕不覆盖(CK)为对照.结果表明:与CK相比,S1、S3、S5、S8和S10处理0～10 cm土层土壤有机碳(TOC)质量分数分别提高7.6％、13.5％、25.4％、48.6％和79.0％:LOC分别提高40.1％、51.5％、102.4％、78.4％和75.3％;CMI分别提高49.4％、61.2％、126.8％、85.4％和75.3％.春玉米产量、全氮、全磷和有效磷分别与LOC和CMI呈极显著相关(P＜0.01),而与TOC无显著相关性.本研究表明,LOC和CMI较TOC更能快速准确地反映不同年限免耕覆盖对土壤碳库和玉米产量的影响,可以作为渭北旱塬免耕秸秆覆盖生态效应的评价指标,且该区覆盖年限以5～8年为宜.     

Artificial neural network and response surface methodology: a comparative analysis for optimizing rice straw pretreatment and saccharification

Abstract

The present study demonstrates a comparative analysis between the artificial neural network (ANN) and response surface methodology (RSM) as optimization tools for pretreatment and enzymatic hydrolysis of lignocellulosic rice straw. The efficacy for both the processes, that is, pretreatment and enzymatic hydrolysis was evaluated using correlation coefficient (R²) & mean squared error (MSE). The values of R² obtained by ANN after training, validation, and testing were 1, 0.9005, and 0.997 for pretreatment and 0.962, 0.923, and 0.9941 for enzymatic saccharification, respectively. On the other hand, the R² values obtained with RSM were 0.9965 for cellulose recovery and 0.9994 for saccharification efficiency. Thus, ANN and RSM together successfully identify the substantial process conditions for rice straw pretreatment and enzymatic saccharification. The percentage of error for ANN and RSM were 0.009 and 0.01 for cellulose recovery and for 0.004 and 0.005 for saccharification efficiency, respectively, which showed the authority of ANN in exemplifying the non-linear behavior of the system.     

Straw utilization for biofuel production: A consequential assessment of greenhouse gas emissions from bioethanol and biomethane provision with a focus on the time dependency of emissions

The shift from straw incorporation to biofuel production entails emissions from production, changes in soil organic carbon (SOC) and through the provision of (co‐)products and entailed displacement effects. This paper analyses changes in greenhouse gas (GHG) emissions arising from the shift from straw incorporation to biomethane and bioethanol production. The biomethane concept comprises comminution, anaerobic digestion and amine washing. It additionally provides an organic fertilizer. Bioethanol production comprises energetic use of lignin, steam explosion, enzymatic hydrolysis and co‐fermentation. Additionally, feed is provided. A detailed consequential GHG balance with in‐depth focus on the time dependency of emissions is conducted: (a) the change in the atmospheric load of emissions arising from the change in the temporal occurrence of emissions comparing two steady states (before the shift and once a new steady state has established); and (b) the annual change in overall emissions over time starting from the shift are assessed. The shift from straw incorporation to biomethane production results in net changes in GHG emissions of (a) ?979 (?436 to ?1,654) and (b) ?955 (?220 to ?1,623) kg CO₂‐eq. per t_{dry matter} straw converted to biomethane (minimum and maximum). The shift to bioethanol production results in net changes of (a) ?409 (?107 to ?610) and (b) ?361 (57 to ?603) kg CO₂‐eq. per t_{dry matter} straw converted to bioethanol. If the atmospheric load of emissions arising from different timing of emissions is neglected in case (a), the change in GHG emissions differs by up to 54%. Case (b) reveals carbon payback times of 0 (0–49) and 19 (1–100) years in case of biomethane and bioethanol production, respectively. These results demonstrate that the detailed inclusion of temporal aspects into GHG balances is required to get a comprehensive understanding of changes in GHG emissions induced by the introduction of advanced biofuels from agricultural residues.     

Effects of different sources of nitrogen on performance,relative population of rumen microorganisms,ruminal fermentation and blood parameters in male feedlotting lambs

Slow-release urea (SRU) can substitute dietary protein sources in the diet of feedlotting ruminant species. However, different SRU structures show varying results of productive performance. This study was conducted to investigate the effect of different sources of nitrogen on performance, blood parameter, ruminal fermentation and relative population of rumen microorganisms in male Mehraban lambs. Thirty-five male lambs with an average initial BW of 34.7 ± 1.8 kg were assigned randomly to five treatments. Diets consisted of concentrate mixture and mineral and vitamin supplements plus (1) alfalfa and soybean meal, (2) wheat straw and soybean meal, (3) wheat straw and urea, (4) wheat straw and Optigen® (a commercial SRU supplement) and (5) wheat straw and SRU produced in the laboratory. No statistical difference was observed in animal performance and DM intake among treatments. The mean value of ruminal pH and ammonia was higher (P < 0.05) for the SRU diet compared with WU diet. The difference in pH is likely to be due to the higher ammonia level as VFAs concentrations were unchanged. The level of blood urea nitrogen (BUN) was different among treatments (P = 0.065). The highest concentration of BUN was recorded in Optigen diet (183.1 mg/l), whereas the lowest value was recorded in wheat straw-soybean meal diet (147 mg/l). The amount of albumin and total protein was not affected by the treatments. The relative population of total protozoa, Fibrobacter succinogenes, Ruminococcus flavefaciens and Ruminococcus albus in the SRU treatment was higher (P < 0.01) than that in urea treatment at 3 h post-feeding. During the period of lack of high-quality forage and in order to reduce dietary costs, low-quality forage with urea sources can be used in the diet. Results of microbial populations revealed that SRU can be used as a nitrogen source which can sustainably provide nitrogen for rumen microorganism without negative effects on the performance of feedlotting lambs.     

秸秆还田配施化肥对土壤肥力及鲜食甘薯产量和品质的影响

通过2017和2018两年的田间试验研究了小麦秸秆还田和施肥对土壤肥力、酶活性以及鲜食甘薯产量和品质的影响。试验设5个处理:秸秆不还田+常规施肥(CK)、小麦秸秆半量还田+常规施肥(50%S)、小麦秸秆全量还田+不施肥(100%S-F)、小麦秸秆全量还田+常规施肥(100%S)、小麦秸秆全量还田+常规施肥+150 kg·hm^-2氮肥(100%S+N)。结果表明:秸秆还田施肥处理显著提高了土壤中的有效磷、碱解氮、总氮和有机质含量,显著提高了土壤过氧化氢酶、碱性磷酸酶、脲酶和蔗糖酶活性。秸秆还田施肥处理均显著提高了薯块产量、单薯鲜重和商品薯率,其中50%S处理下薯块产量最低。2年的秸秆还田处理下,薯块产量和商品薯率均在100%S处理下最高。2年的秸秆还田施肥处理总体上提高了甘薯的淀粉和蛋白质含量,但100%S和100%S+N处理均降低了甘薯还原糖和可溶性糖含量。可见,小麦秸秆全量还田的效果优于半量还田,与常规施肥配合下薯块产量和商品薯率最高,但影响食用口感,实际生产中可适当减少氮肥用量。