Secretome analysis of thermophilic mould Myceliophthora thermophila cultivated on rice straw and hydrolysis of lignocellulosic biomass for bioethanol production

Abstract

Myceliophthora thermophila encodes for large number of carbohydrate-active enzymes (CAZymes) involved in lignocellulosic biomass degradation. The mould was grown on rice straw in solid state fermentation at pH 5.0 and 45?°C that produced high levels of cellulolytic and xylanolytic enzymes i.e. 2218.12, 515.23, 478.23, 13.34?U/g DMR for xylanase, CMCase, FPase and β-glucosidase, respectively. The secretome analysis of M. thermophila BJAMDU5 by mass spectroscopy, described 124 different proteins with majority of CAZymes consisting of glycosyl hydrolases (GH), lytic polysaccharide mono-oxygenases (LPMO), carbohydrate esterases (CE) and polysaccharide lyases (PL). Furthermore, the enzyme cocktail of the mould was evaluated for hydrolysis of steam treated rice straw that produced 184.59?mg/g substrate reducing sugars after 24?h, which was used for production of bioethanol by using fast fermenting yeast Saccharomyces cerevisiae resulting in high production of bioethanol.     

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.     

乙醇对瘤胃液接种稻秸的体外发酵产物及细菌群落结构的影响

旨在研究乙醇对山羊瘤胃液与水稻秸秆厌氧共培养的影响。利用频繁传代的体外发酵技术和高通量测序方法,分析了短链脂肪酸(SCFA)产量和细菌群落的变化。结果表明,经体外培养传代8次的稻秸发酵液的总短链脂肪酸产量显著高于瘤胃液(P<0.01);与未添加乙醇的稻秸发酵液相比,添加乙醇显著提高了乙酸、戊酸和己酸的比例,降低了丙酸和丁酸的比例(P<0.01),总SCFA产量及异丁酸和异戊酸比例无显著差异。与瘤胃液相比,稻秸发酵液的拟杆菌门(Bacteroidetes)相对丰度下降,厚壁菌门(Firmicutes)相对丰度升高(P<0.05),且添加乙醇显著提高了厚壁菌门和放线菌门(Actinobacteria)的相对丰度(P<0.05);添加乙醇使双歧杆菌属(Bifidobacterium)、未定性的毛螺菌属(unidentified Lachnospiraceae)、产琥珀酸菌属(Succiniclasticum)、脱硫弧菌属(Desulfovibrio)和未定性的梭菌属(unidentified Clostridiales)的相对丰度显著升高(P<0.05)。乙醇使稻秸发酵液的显著性差异物种(Biomarker)增加;稻秸发酵液与瘤胃液亲缘关系较近,而添加乙醇显著改变了细菌区系;短链脂肪酸比例在稻秸发酵液细菌群落多样性中具有重要作用。研究表明,体外频繁传代和添加乙醇可以提高稻秸发酵液的乙酸、戊酸和己酸产量,乙醇改变了稻秸发酵液的细菌群落结构。     

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.     

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 method of straw disposal and depth of cultivation on populations of Fusarium spp. in soil and on brown foot rot in continuous winter wheat

Soil samples (0–10 cm depth) taken from plots of continuous winter wheat at intervals between January 1993 and July 1996 were dilution-plated on PCNB agar to identify and enumerate colony-forming units (cfus) of Fusarium spp. Cfus of the main wheat pathogen, F. culmorum, were more numerous in soil from plots that were shallow-cultivated to 10 cm after each harvest than in those that were ploughed. They were also usually more numerous in plots in which straw had been chopped and incorporated (by shallow cultivation or ploughing) than in those in which straw had been burnt. Increasing amounts of straw tended to increase the number of cfus. Deeper sampling (15–25 cm) showed that ploughing resulted in a more even, but diluted, distribution of cfus down the soil profile. Populations of some commonly found species that are not pathogenic on wheat {F. oxysporum, F. equiseti, F. flocciferum and F. merismoides) were sometimes also affected by straw disposal or cultivation treatments. Alternative methods of estimating population densities (baiting soil with wheat kernels or wheat seedlings, or plating-out straw fragments) showed generally similar effects of treatments on populations of F. culmorum; the relative merits of the methods are considered. Large differences in population densities of all species occurred within and between seasons. The smallest populations were found in January 1995 but, in the case of F. culmorum, they increased to relatively large numbers in July 1995. The summer of 1995 was warm and dry and especially favourable for development of fusarium foot rot. Severe disease occurred only in this year and was less frequent after ploughing than after tine-cultivation but more frequent after straw burning than after straw incorporation. The implications of these observations for understanding the role of propagules of F. culmorum in soil as inoculum for foot rot are discussed.     

Screening of white‐rot fungi for bioprocessing of wheat straw into ruminant feed

Aim

In this study, the biological variation for improvement of the nutritive value of wheat straw by 12 Ceriporiopsis subvermispora, 10 Pleurotus eryngii and 10 Lentinula edodes strains was assessed. Screening of the best performing strains within each species was made based on the in vitro degradability of fungal‐treated wheat straw.

Methods and Results

Wheat straw was inoculated with each strain for 7 weeks of solid state fermentation. Weekly samples were evaluated for in vitro gas production (IVGP) in buffered rumen fluid for 72 h. Out of the 32 fungal strains studied, 17 strains showed a significantly higher (P < 0·05) IVGP compared to the control after 7 weeks (227·7 ml g^?1 OM). The three best Ceriporiopsis subvermispora strains showed a mean IVGP of 297·0 ml g^?1 OM, while the three best P. eryngii and L. edodes strains showed a mean IVGP of 257·8 and 291·5 ml g^?1 OM, respectively.

Conclusion

Ceriporiopsis subvermispora strains show an overall high potential to improve the ruminal degradability of wheat straw, followed by L. edodes and P. eryngii strains.

Significance and Impact of the Study

Large variation exists within and among different fungal species in the valorization of wheat straw, which offers opportunities to improve the fungal genotype by breeding.     

不同秸秆填埋量对盐碱土水盐运移及垂柳反射光谱的影响

在宁夏西北盐化生态脆弱区的典型盐碱化土地,通过随机区组试验,探究在栽植穴填埋秸秆2000(T_1)、7000(T_2)、12000kg/hm~2(T_3)及17000 kg/hm~2(T_4)等作隔盐层对土壤水盐运移及垂柳(Salix babylonica)反射光谱的影响,将地下土壤水盐变化与地上植物生长及生理状况相结合,以期更准确的反映出各处理对盐碱土壤改良效果及地上植被恢复情况。研究结果表明:(1)填埋一定量的秸秆作隔盐垫层可以改变地下土壤水盐的剖面分布特征。T_2、T_3和T_4处理与对照组相比,20—80 cm土层土壤含水量都显著提高,填埋的秸秆层起到了蓄水保墒的作用;都明显降低了0—80 cm土层土壤盐分含量和盐溶质浓度;但这3种处理之间无显著差别。T_1由于填埋秸秆量过少,无显著蓄水控盐效果。(2)通过检测植物叶片反射光谱可以反映出地上植物生长及生理状况的变化。填埋一定量的秸秆作为隔盐垫层有助于改善垂柳的生理状况。T_2的垂柳叶片光合色素含量最高,光合特性及营养状况最好,其他光谱参数结果都显著提高。T_3显著提高叶绿素含量和光合特性,但效果均不如T_2,且营养状况差。T_4处理类胡萝卜素含量与叶片水分含量均处于最高水平,但叶绿素含量、营养状态以及光合特性都显著降低。T_1处理效果最差。(3)在地下填埋秸秆作隔盐层,会通过对地下土壤水盐运移及微域生态系统环境的调节,影响到地上植物生长及生理状况。综合地下水盐分布与地上植物叶片反射光谱的结果,T_2是宁夏引黄灌区盐碱地改良中最适宜的秸秆填埋量。     

秸秆和地膜覆盖对渭北旱作玉米农田土壤氮组分与产量的影响

基于田间定位试验,研究了秸秆和地膜覆盖措施对旱作春玉米田土壤氮组分和作物产量的影响。试验包括无覆盖对照,秸秆覆盖和地膜覆盖3个处理,观测指标包括土壤全氮(STN)、颗粒有机氮(PON)、潜在可矿化氮(PNM)、微生物量氮(MBN)、硝态氮(NO_3~--N)、铵态氮(NH_4~+-N)含量及作物产量。结果表明:试验进行5到7年后,与对照相比,秸秆覆盖处理0—10 cm土层STN、PON、PNM、MBN和NO_3~--N含量3年平均分别提高了13.11%、64.29%、17.51%、16.94%和55.37%,10—20 cm土层STN、PON、MBN和NO_3~--N含量3年平均分别提高了5.93%、33.33%、15.78%和27.57%(P0.05)。而地膜覆盖处理0—10 cm和10—20 cm土层NO_3~--N的含量较对照分别提高了189.14%和135.75%(P0.05),其他氮组分与对照处理差异不显著。秸秆和地膜覆盖处理玉米产量较对照处理3年平均分别提高了6.90%和36.74%(P0.05)。玉米产量与0—20 cm土层NO_3~--N含量和NO_3~--N/STN值呈显著正相关关系。总的来看,秸秆覆盖能显著增加旱地土壤全氮和活性有机氮含量,促进氮素固定,但需注意作物生长后期补充氮肥以满足作物生长需要。而地膜覆盖能显著提高土壤氮素有效性和作物产量,但不利于土壤有机氮的固定,且表层土壤存在潜在氮淋失风险。     

汉中盆地秸秆还田撂荒和林地对土壤碳的影响

农业活动是温室气体重要的排放源,土壤碳库[土壤有机碳(SOC)和无机碳(SIC)]稍微变化会对大气CO_2产生很大影响。汉中盆地是南水北调的重要水源涵养地,在该区域秸秆还田、农田撂荒和林地是目前常见土地利用方式,但缺乏不同利用方式对SIC和SOC影响的研究。该研究采集该区域典型样地土壤,用滴定法和有机碳分析仪分别测定其SIC和SOC含量,研究3种土地利用方式对土壤碳库的影响。结果表明:SOC随土层深度最为敏感的是农田,其次是撂荒地,林地最不敏感。0~140 cm土层SOC碳密度,林地最大,是撂荒田的2.26倍,农田是撂荒田的1.37倍。深土层SOC碳密度,林地是撂荒田的2.44倍,农田是撂荒田的1.07倍。撂荒田的SIC密度最大,其次是农田,林地的SIC碳密度最低。在0~140 cm土层中,SIC密度依次为12.37、11.68和9.77 kg·m~2,撂荒田的SIC碳密度是林地的1.27倍。随着我国农村发展,土地利用管理出现新的方式,今后在估算土地利用管理方式对土壤碳影响时还需要综合考虑SOC和SIC。