微贮干玉米秸秆和废弃物单相厌氧共消化产沼气能力分析

以干玉米秸秆和剩余污泥/猪粪作为发酵原料对预处理方式和厌氧消化工艺进行研究,旨在为现代沼气工程稳定运行提供一定的科学依据。以芽孢杆菌和乳酸菌等微生物进行复配对干玉米秸秆进行微贮预处理,研究秸秆微贮前后的组成变化及微生物多样性,在此基础上考察两相和单相厌氧消化对原料发酵沼气产量的影响,最后采用微贮秸秆和剩余污泥/猪粪进行厌氧共消化以进一步提高沼气产率。结果表明,微贮秸秆pH值降低,有机酸浓度提高,纤维素得到有效保护未被降解;微贮原料中乳酸菌为优势菌群;微贮秸秆两相和单相厌氧消化累积沼气产量分别达到292.06和411.46 mL/g TS;微贮秸秆和剩余污泥/猪粪按照比例混合进行单相厌氧共消化,累积沼气产量分别达到500.97和599.39 mL/g TS,为提高干玉米秸秆和剩余污泥/猪粪混合发酵产气量和发酵效率提供参考。     

两相厌氧工艺在制糖废水处理中的应用

由于两相厌氧工艺具有产酸相与产甲烷相分离的特性,因此在处理具有高有机负荷、高悬浮物浓度（SS）的制糖废水方面具有独特的优势。针对制糖废水的特征、传统的治理技术进行了论述,并对两相厌氧工艺在处理制糖废水方面所存在的独特优势进行了分析。     

纤维素酶用量和底物浓度对玉米秸秆酶解的影响

首先采用碱液湿磨法对玉米秸秆进行预处理,然后对预处理玉米秸秆进行酶解,调查了纤维素酶用量、底物浓度对还原糖收率和反应速度的影响,同时讨论了木质素对纤维素酶解的抑制机理。纤维素酶用量在1.5～30FPU/g的范围内变化,底物浓度在10～40g/L的范围内变化。通过对预处理玉米秸秆酶解的响应面分析,得到了还原糖收率与纤维素酶用量、底物浓度之间的关系式。实验结果表明,纤维素酶用量越大,酶解反应速率随底物浓度的增加幅度也越大。木质素对纤维素酶的吸附会造成纤维素酶的失活,从而导致酶解反应速率和还原糖收率的降低。     

NaOH-H2O2溶剂体系下玉米秸秆的组分分离规律研究

研究了NaOH-H2O2组成的碱溶剂体系对玉米秸秆的溶解规律,并结合酸沉、醇析方法分离出了3种主要成分,研究了过氧化氢浓度、pH、液固比、温度、时间对玉米秸秆组分分离过程的影响。结果表明:碱溶剂处理后的剩余固体物质是纤维素和不溶物,滤液经酸沉后的固体为木质素,酸沉后的滤液调pH后醇析所得的固体为半纤维素。试验确定了分离过程的最佳工艺条件:过氧化氢浓度5%,pH=12,反应时间3 h,溶解温度60℃,液固比30 m L/g。在此条件下,纤维素回收率84.2%,木质素回收率为66.6%,半纤维素回收率96.7%,滤液经4次循环使用,纤维素回收率82.7%,木质素回收率67.6%,半纤维素回收率97.4%。碱处理及酸沉、醇析后剩余固体的结构分析证明了此方法的可行性。     

利用分散染料废水的硫酸铵自动连续化制备

针对分散染料酸性废水难处理、易再次污染等问题,以分散蓝291∶3滤饼生产过程中产生的酸性母液废水为例,研究了酸性分散染料废水综合循环利用及资源化技术,并探索染料废水节能减排技术的工艺过程。分散蓝291∶3酸性母液废水经中和、脱色和分离、精滤、机械蒸汽再压缩(MVR)浓缩结晶、离心分离等工艺处理后,残余染料等有机物基本脱除,得到了氮含量在20.92%以上,游离酸(硫酸)含量低于0.1%的硫酸铵产品,从而实现了染料废水的循环利用和资源化。整个处理工艺实现了硫酸铵的自动连续化和清洁高效生产,同时MVR蒸发浓缩技术循环利用了它自身产生的二次蒸汽能量,提升了制备硫酸铵的经济效益和环保效益。     

靛蓝生产废水中有机物脱除研究

研究了铁炭内电解法对靛蓝生产废水COD去除率和脱色率的影响.结果表明:室温、质量浓度为15000mg/L的废水在铁炭比为0.15:1、反应流速1BV/h、铁屑粒径3.5～4mm、活性炭为小颗粒时,COD去除率和脱色率分别达到78.12%和78.81%,该内电解柱的穿透体积为9BV,使用周期5次.铁炭内电解法与纯活性炭柱吸附法、活性炭搅伴吸附法相比有较大优势,为后续的混碱回收操作提供了良好条件.     

Pilot-scale production of low molecular weight peptides from corn wet milling byproducts and the antihypertensive effects in vivo and in vitro

A pilot-scale production was developed to enhance the value of proteins from corn gluten meal (CGM). Corn protein isolate (CPI) with high protein content (90.68%) was obtained through heat treatment of CGM (150 kg) in aqueous alkaline solution. Two-step enzymatic hydrolysis and multistage separation were applied to enrich corn oligopeptides (COP) with low molecular weights, 96.77% of which were less than 1000 Da. The greatest antihypertensive effect of COP treatment in spontaneously hypertensive rats (SHR) was observed at a dose of 0.45 g/kg. One major ACE-inhibitory peptide, Ala-Tyr, was identified and quantified (9.16 ± 0.08 mg/g) from COP. The ACE inhibitory activity of Ala-Tyr (IC₅₀ = 0.037 mg/ml) was over 27 times higher than that of COP (IC₅₀ = 1.020 mg/ml). The results indicate that COP may be a source of natural antihypertensive compounds that could be used for drugs or functional food ingredients.     

体外产气法评定青贮玉米秸与豆秸组合的瘤胃发酵特性

探讨青贮玉米秸与豆秸组合对瘤胃发酵参数的影响,以确定适宜的饲料组合比例。本试验将青贮玉米秸与豆秸分别按0∶100、20∶80、40∶60、60∶40、80∶20、100∶0的比例进行组合,利用体外瘤胃发酵技术,分析不同比例组合对产气量、pH值、氨态氮、菌体蛋白和瘤胃干物质、中性洗涤纤维和酸性洗涤纤维的影响,并计算出各组合的单项组合效应值和综合组合效应值,进而筛选出两种饲料组合的适宜比例。结果表明：青贮玉米秸-豆秸不同比例组合后在产气量上差异显著（P〈0.05）,以80∶20时最大;各比例对体外瘤胃液pH值影响差异不显著（P〉0.05）;氨态氮质量浓度随青贮玉米秸比例的增加而增加,在40~50mg/dl变化;菌体蛋白质量浓度在两者比例为80∶20时最高;青贮玉米秸-豆秸不同比例组合的干物质、中性洗涤纤维和酸性洗涤纤维的瘤胃有效降解率均以80∶20时最大。在本试验条件下,以多项组合效应评定指数评定组合效应,青贮玉米秸与豆秸比例为80∶20时较为适宜,综合组合效应指数达到最大。     

New ecological nixtamalisation process for tortilla production and its impact on the chemical properties of whole corn flour and wastewater effluents

An ecological nixtamalisation process (EP) for making whole corn flour for tortillas was compared with the traditional nixtamalisation process (TP). One of the problems of TP is high level of solid losses. The aim was to evaluate the composition of these losses. In EP, dry matter losses of nejayote were from 1.2% to 1.4%, while in TP 3.2%. Nejayote from TP showed a pH of 11.9, whereas EP showed a pH close to neutral. The pericarp was retained in EP with the use of calcium salts, whereas in TP lime destroyed it almost completely. Losses of total dietary fibre in nejayote solids were about 41.2% for TP compared to an average of 17.4% for EP. Most of nejayote losses in TP were soluble fibre (30.4%), compared with EP that ranged from 6.2% to 7.9%. All compounds retained by nixtamal from EP are important sources of nutrients and dietary fibre.     

Short communication: influence of the muscle hypertrophy mutation of the myostatin gene on milk production traits and milk fatty acid composition in dual-purpose Belgian Blue dairy cattle

The objective of this study was to estimate genetic effects for the muscle hypertrophy mutation (mh) of the myostatin gene for conventional milk production traits and for milk fatty acid composition in dual-purpose Belgian Blue dairy cows. For the present study, only cows from a single herd, in which genotype frequencies were as balanced as possible (0.266 for +/+, 0.523 for mh/+, and 0.211 for mh/mh), were chosen to avoid confounding between herd and genotype effects. A total of 109 cows with 3,190 test-day records for fat, protein, and milk yields and 1,064 test-day records for saturated and monounsaturated fatty acids were used for the calculations. Variance component and gene effect estimations were performed via expectation-maximization REML and BLUP methods, respectively, using a multi-trait mixed test-day model with an additional fixed regression on the muscle hypertrophy genotype. Results showed that one copy of the wild-type “+” allele led to a significant additive effect of 26.35 g/d for fat yield. Significant dominance effects of 23.22 g/d for protein yield and 30.28 g/d for fat yield were also observed. In contrast, a nonsignificant trend was observed in favor of lower saturated fatty acid contents in milk for one copy of the mutant “mh” allele. Concerning milk, fat, and protein yields, our results confirmed literature results indicating a superior effect of the “+” allele compared with the mutant allele. Therefore, the selection of the “+” allele has the potential to increase conventional milk production traits in the dual-purpose Belgian Blue breed. However, when focus is given to milk fatty acid profile, a possible antagonistic effect between the benefit of the “+” allele for higher milk production and the “mh” allele for reduced saturated fatty acid content in milk should be confirmed in further studies.     

Effects of corn silage derived from a genetically modified variety containing two transgenes on feed intake, milk production, and composition, and the absence of detectable transgenic deoxyribonucleic acid in milk in Holstein dairy cows

The objectives were to compare the chemical composition, nutritive value, feed intake, milk production and composition, and presence in milk of transgenic DNA and the encoded protein Cry1Ab when corn silages containing 2 transgenes (2GM: herbicide tolerance: mepsps and insect resistance: cry1Ab) were fed as part of a standard total mixed ration (TMR) compared with a near isogenic corn silage (C) to 8 multiparous lactating Holstein dairy cows in a single reversal design study. Cows were fed a TMR ration ad libitum and milked twice daily. Diets contained [dry matter (DM) basis] 45% corn silage, 10% alfalfa hay, and 45% concentrate (1.66 Mcal of net energy for lactation/kg of DM, 15.8% crude protein, 35% neutral detergent fiber, and 4.1% fat). Each period was 28-d long. During the last 4 d of each period, feed intake and milk production data were recorded and milk samples taken for compositional analysis, including the presence of transgenic DNA and Cry1Ab protein. There was no significant difference in the chemical composition between C and 2GM silages, and both were within the expected range (37.6% DM, 1.51 Mcal of net energy for lactation/kg, 8.6% crude protein, 40% neutral detergent fiber, 19.6% acid detergent fiber, pH 3.76, and 62% in vitro DM digestibility). Cows fed the 2GM silage produced milk with slightly higher protein (3.09 vs. 3.00%), lactose (4.83 vs. 4.72%) and solids-not-fat (8.60 vs. 8.40%) compared with C. However, the yield (kg/d) of milk (36.5), 3.5% fat-corrected milk (34.4), fat (1.151), protein (1.106), lactose (1.738), and solids-not-fat (3.094), somatic cell count (log₁₀: 2.11), change in body weight (+7.8 kg), and condition score (+0.09) were not affected by type of silage, indicating no overall production difference. All milk samples were negative for the presence of transgenic DNA from either trait or the Cry1Ab protein. Results indicate that the 2GM silage modified with 2 transgenes did not affect nutrient composition of the silages and had no effect on animal performance and milk composition. No transgenic DNA and Cry1Ab protein were detected in milk.     

Part III: the influence of serial repitching of Saccharomyces pastorianus on the production dynamics of some important aroma compounds during the fermentation of barley and gluten‐free buckwheat and quinoa wort

The present paper is the last report of a comprehensive study regarding the influence of the serial repitching of Saccharomyces pastorianus TUM 34/70 on the composition of a barley, buckwheat or quinoa fermentation medium. In particular, it focuses on the production dynamics of important volatile compounds typically associated with the aroma of beer. Samples were taken every 24 h after 11 serial repitchings of a single starter culture, analysed for the particular aroma compound content by distillation followed by gas chromatography with flame ionization detection. The term ‘serial repitching factor’ is used for the first time to support the visual evaluation of the influence of serial repitching. Results showed that the levels of methanol in the quinoa wort fermentation were only slightly higher than in barley and in practical terms independent of successive fermentation. The behaviour of acetaldehyde in quinoa was similar to that in barley. However, there was a final 2‐fold lower production of some important aroma compounds compared with barley and buckwheat and for this reason quinoa cannot be recommended as a gluten‐free substitute to produce a bottom‐fermented beer. Regarding the buckwheat wort fermentation, a 2‐ to 3‐times lower final acetaldehyde content than in barley is desirable, whereas a relatively high methanol content is not desirable. Barley and buckwheat showed comparable sum concentrations and similar overall profiles of some important aroma compounds. From this perspective, buckwheat appears to be a promising substitute for barley as a brewing raw material. The overall conclusions of our comprehensive study (Parts I–III) are that buckwheat shows adequate brewing properties to substitute for barley in the commercial preparation of a bottom‐fermented gluten‐free beer‐like beverage, and yeast can be repitched at least 11 times. In contrast, quinoa in practical terms shows no substitutional potential for barley in beer; however, it has many nutritious advantages, thus the commercial preparation of a unique, bottom‐fermented gluten‐free ‘non‐beer‐like’ beverage – where the yeast could be repitched six times at most – appears feasible. Copyright © 2015 The Institute of Brewing & Distilling