粒径对好氧颗粒污泥储存稳定性的影响

研究了混合粒径与不同粒径好氧颗粒污泥（AGS）在储存过程中的三维结构、质量变化、微生物活性以及理化特性的变化规律。经过室温（16~25℃）下31天的储存,污泥的三维结构均保持较好,未出现明显解体现象。混合粒径的AGS在储存前20天,其质量和比耗氧速率（SOUR）下降缓慢,胞外聚合物（EPS）先减小后上升。20天之后由于厌氧菌在竞争中逐渐占得优势,其质量减小了46.3%,EPS与SOUR分别下降69.0%和72.7%,导致稳定性随之下降。不同粒径AGS经过储存后,其颜色仍为橙黄色且结构完整;1~2mm和3~4mm粒径的AGS质量减小（分别为49.1%和53.9%）较大,且SOUR和EPS下降了亦较大;0.3~1mm粒径的AGS质量减小较少,EPS下降较少,但SOUR下降幅度较大,而2~3mm粒径的质量仅减小了33.7%、SOUR下降幅度最小（39.8%）,EPS下降幅度也相对较小（58.7%）,表明其在储存过程中能保持较好的活性与稳定性。     

一株有氧条件下高产乙醇酵母的筛选、鉴定及其生物学特性研究

采用平板涂布法从老白干香型大曲中获得一株有氧条件下高产乙醇酵母菌株,命名为YF1914。通过菌落形态、细胞显微结构、生理生化特性和26S rDNA D1/D2区方法对其进行鉴定,借助液体培养方式考察其乙醇耐受性、葡萄糖耐受性、乙酸耐受性、生长温度和pH等生物学特性。结果表明,该菌株为酿酒酵母(Saccharomyces cerevisiae)属于乙醇高耐受性酵母,耐受乙醇最高体积分数为18%,同时还具有较高的NaCl和葡萄糖耐受性,最高耐受质量分数分别为15%和80%,在温度为20~50 ℃和pH1~10能够生长,具有宽广的温度和pH适应性。综上,该酵母这些优良特性有利于其在未来白酒酿造方式变化中发挥作用。     

低温杀菌黄焖鸡中菌落总数生长预测模型的比较和货架期预测

为比较不同生长预测模型对低温杀菌黄焖鸡中菌落总数生长情况的拟合效果,使用修正的Gompertz模型、修正的Logistic模型和Baranyi模型描述其在4、15、25 ℃贮藏期间菌落总数的变化情况,使用Belehradek模型和Arrhenius模型描述菌落总数生长参数与贮藏温度之间的关系,通过计算各模型拟合所得的参数值及回归相关系数R2、均方误差平方根、赤池信息准则和贝叶斯信息准则等指标评价模型的拟合优度,以最优组合建立产品的货架期预测模型。结果表明：在一级模型中,修正的Logistic模型拟合所得的生长参数值最接近实测值,模型的评价指标最优;在二级模型中,Arrhenius模型的拟合优度最高,其R2均在0.97以上;对修正的Logistic模型的偏差因子、准确因子和Arrhenius模型的残差值进行分析,表明建立的一级、二级模型可被接受;以此为基础建立低温杀菌黄焖鸡的货架期预测模型,经过验证,模型预测值与实测值的相对误差值均在±10%以内,表明所建立的货架期预测模型能够比较准确地预测低温杀菌黄焖鸡在4～25 ℃范围内的货架期。     

微好氧与厌氧水解酸化对明胶废水的预处理效果

以明胶废水为研究对象,采用微好氧与厌氧水解酸化工艺进行对比处理实验,探讨了不同水力停留时间下微好氧与厌氧水解酸化对明胶废水水质改善的效果。实验结果表明,在水力停留时间达到72 h的时候,溶解氧为1.3~1.6 mg/L的微好氧反应器的COD去除率最大可达25%,溶解氧为0.3~0.5 mg/L的厌氧反应器的COD去除率最大可达22%;微好氧反应器的VFA的含量达到12 mg/L左右,厌氧反应器只有8 mg/L左右;微好氧反应器的pH值可由最初的12.5降至7.5左右,而厌氧反应器只能降至8.0左右;两个反应器对蛋白质去除效果的差别并不明显,都可以达到90%以上,但是微好氧反应器的氨氮浓度只有22 mg/L,小于厌氧反应器中的氨氮浓度,说明微氧条件有利于氨氮的扩散挥发,低浓度的氨氮对微生物的危害较小。对比得出微好氧反应器的出水水质较好,更适合明胶废水水解酸化的预处理。     

微生物颗粒在废水处理中的应用与研究

微生物颗粒是微生物在适当的环境条件下,相互聚集形成的自聚集体。由于微生物颗粒具有良好的生物活性、沉降速度快、无需载体、易于固液分离等许多优点,在废水处理中得到了广泛的研究与应用。微生物颗粒化是一个复杂的过程,受多种因素影响。作者对近些年来国内外的一些研究成果,从厌氧颗粒污泥、好氧颗粒污泥、菌丝球3个方面综述了微生物颗粒在废水处理中的研究进展,内容包括颗粒的基本特性、微生物相,主要影响因素及其颗粒化过程。     

连续流与序批式组合运行启动高性能CANON反应器

在完全混合流反应器中接种亚硝化颗粒污泥,通过分阶段使用连续流和序批式运行方式,成功启动了全自养生物脱氮（CANON）工艺,并对反应器性能、污泥形态与活性、微生物菌群结构的变化规律进行了深入分析。结果表明,基于初始连续流运行获得的良好基质比,序批式阶段的高氨氮负荷和高溶解氧条件可有效促进污泥浓度与活性的增长,使得反应器在最终连续流状态下的总氮去除负荷达到了1.75 kg·（m³·d）^-1。运行期间,颗粒污泥的密实度和沉降性能均得到改善。由Miseq高通量测序的结果可知,CANON颗粒污泥具有相对较高的微生物多样性。对应于总氮比去除速率0.24 g·（g VSS·d）^-1,Nitrosomonas（好氧氨氧化菌）与Candidatus Kuenenia（厌氧氨氧化菌）丰度比值约为3：1。少量贫营养型亚硝酸盐氧化菌对CANON工艺没有显著影响。     

An evaluation of the effectiveness of a chemical additive based on sodium benzoate,potassium sorbate,and sodium nitrite on the fermentation and aerobic stability of corn silage

We evaluated the effectiveness of an additive comprising sodium benzoate, potassium sorbate, and sodium nitrite (SSL) as active ingredients for its ability to improve the aerobic stability of corn silages made in North America. In experiment 1, treatment with SSL (1.5 and 2.0 L/t) on whole-plant corn (WPC) was compared with treatment with an additive containing buffered propionic acid and citric acid (BPA; 2 L/t) on corn harvested at 32 and 38% dry matter and ensiled for 120 d. Silage treated with BPA was higher in ammonia-N and propionic acid relative to other treatments. Treatments with all of the additives had numerically, but not statistically, fewer yeasts compared with untreated silage. Both application rates of SSL resulted in lower concentrations of ethanol compared with untreated and BPA silages. Treatment with BPA improved the aerobic stability of silages compared with untreated silage, but the effect from SSL was markedly greater. In experiment 2, WPC was untreated or treated with 2 or 3 L of SSL/t or a microbial inoculant containing Enterococcus faecium M74, Lactobacillus plantarum CH6072, and Lactobacillus buchneri LN1819 (final total lactic acid bacteria application rate of 150,000 cfu/g of fresh forage). Silages were air stressed for 24 h at 28 and 42 d of storage and ensiled for 49 d before opening. Inoculation had no effect on acid end products, ethanol, number of yeasts, or aerobic stability compared with other treatments. Treatment with SSL decreased the amount of ethanol, had no effect on number of yeasts, and improved aerobic stability in a dose-dependent manner compared with other treatments. In experiment 3, WPC was untreated or treated with 2 L of SSL/t and ensiled for 5, 15, and 30 d. Treatment with SSL resulted in silage with fewer yeasts and lower concentrations of ethanol after all times of ensiling compared with untreated silage. In addition, SSL improved aerobic stability after each period of ensiling, but the effect was more at 15 and 30 d compared with 5 d of storage. Treating WPC with SSL can improve the aerobic stability of corn silage made in North America, and the effect can be observed as soon as 5 d after ensiling.     

Silage review: Recent advances and future technologies for baled silages

Although the concept of ensiling large-round or large-square bales dates back to the late 1970s, many refinements have been made to both equipment and management since that time, resulting in much greater acceptance by small or mid-sized dairy or beef producers. This silage preservation technique is attractive to producers for several reasons, but the primary advantage is a reduced risk of weather damage to valuable forage crops compared with preservation as dry hay. Most core principles for making high-quality precision-chopped silages also apply to baled silages; among these, establishing and subsequently maintaining anaerobiosis are priorities. For baled silages, these priorities are critical, in part because recommended moisture concentrations (45 to 55%) are drier, and particle length is much longer. These factors act to restrict the rate and extent of silage fermentation, often resulting in less production of desirable fermentation acids and a greater (less acidic) final pH. Within this context, preservation of baled silages can be improved by applying polyethylene (PE) film wraps promptly, using an appropriate number of PE film layers (6 to 8), selecting a storage site free of sharp objects or other debris, and by monitoring wrapped bales closely for evidence of puncture, particularly by birds or vermin. Under certain conditions, such as those in which the bale moisture of highly buffered forages exceeds the recommended range, the heterogeneous nature of baled silages coupled with a restricted rate and extent of fermentation may increase susceptibility to clostridial activity compared with precision-chopped forages ensiled at comparable moisture concentrations. To date, research evaluating inoculants or other additives designed to improve the fermentation of challenging forages or aerobic stability has been limited, but should not be discontinued. Development of PE film embedded with an oxygen-limiting barrier has yielded positive results in some trials; however, most differences between these novel formulations and reputable commercial PE film have been related to decreases in yeast and mold counts at the surface layer. Related assessments of fermentation or nutritive value determined on a whole-bale basis have been less conclusive. Baled silages can be produced successfully by adhering to straightforward management principles; as such, this form of silage production is likely to remain popular for the foreseeable future.     

Silage review: Factors affecting dry matter and quality losses in silages

An overview was made of dry matter (DM) and quality losses that occur during the ensiling process from the field through the feeding phase. The aim was to review the relevant published literature of the last 15 yr focusing on developments achieved after the publication of the book Silage Science and Technology. This review discusses the factors affecting DM and quality losses in terms of field and pre-ensiling conditions, respiration and temperature at ensiling, fermentation patterns, methods of covering and weighting the silage cover, and management of aerobic deterioration. The possibility of reducing DM and quality losses during the ensiling process requires knowledge of how to measure losses on farm and establish the status of the silage during the feed-out phase, implementing the most effective management practices to avoid air exposure during conservation and reduce silage aerobic deterioration during feeding. The paper concludes with future perspectives and recommended management practices to reduce losses and increase efficiency over the whole ensiling process in view of increasing sustainability of the livestock production chain.