米曲霉、黑曲霉和绿色木霉混合发酵马铃薯废渣生产细胞蛋白的研究

本文将米曲霉、黑曲霉和绿色木霉三种霉菌复配,研究复配菌对马铃薯废渣的分解能力和各复配菌之间的相互作用关系。试验结果表明:三种霉菌按照1:1复配,出现四种复配结果,其中利用马铃薯废渣转化成饲料蛋白效果最好的是黑曲霉和米曲霉的复配菌,在120h内能将马铃薯废渣完全分解,且蛋白质收率最高,达到8.292g/L,高于单菌发酵蛋白质的收率(7.775g/L),将粗蛋白质的收率提高了2.59倍。此外,通过研究复合菌和单菌发酵液中总糖和还原糖的含量变化,推断出各混合菌之间的相互作用关系:黑曲霉与绿色木霉之间是互惠共生关系;米曲霉与黑曲霉是竞争关系,而且黑曲霉在分解利用马铃薯废渣的过程中占竞争优势;绿色木霉对米曲霉利用马铃薯废渣有抑制作用;三种菌混合发酵马铃薯废渣时,黑曲霉的生长占竞争优势。     

两种曲霉发酵米渣生产酱油的研究

本文介绍了以米渣为主要原料，采用曲霉进行圆态制曲，液态无盐发酵酿造酱油主要工艺流程，最佳种曲，成曲培养其配方和最适工艺条件。试验结果发明：发酵周期缩短至３－４天，原料全氮利用率达８０％以上，氨基酸生成率达５８％，本工艺适用可行，具有较高的社会和经济效益。     

米曲霉发酵牛乳工艺条件的研究

利用米曲霉对牛乳进行发酵,通过单因子及正交试验以菌丝体干重、氨基酸态氮为考察指标对其发酵牛乳工艺条件进行了研究。结果表明,发酵是在pH值自然状态下,接种量为5%,装液量为25mL,摇床转速为180r/min时,菌丝体干重可达到2.71g/100mL。氨基酸态氮达0.3088g/100mL。     

马铃薯渣酸水解工艺条件的研究

针对马铃薯渣中不溶性的碳水化合物,采用硫酸热水解法使其中的淀粉、纤维素、半纤维素等成分在以硫酸做催化剂的条件下水解成还原性糖。在酸浓度、酸固比、水解时间、水解温度四个单因素实验基础上,采用正交实验设计优化工艺条件。结果表明,在酸浓度为32%,酸固比为3∶1,水解时间为1h,水解温度为90℃下,1g马铃薯渣经水解上清液中总还原糖重量最高为0.5213g。      

米曲霉产氨肽酶发酵条件优化

该文对1株产氨肽酶的米曲霉产酶条件进行单因子优化。确定产酶培养基和培养条件为:2%黄豆粉、0.3%K2HPO4,0.2%油酸,初始pH 5.0。在30℃,200 r/min下液体培养48 h后胞外酶活达497.13 U/mL,较优化前提高了3倍以上。该米曲霉营养要求简单,氨肽酶产量高,发酵周期短,非常适于生产研究。     

米曲霉发酵大豆多肽工艺条件研究

以大豆分离蛋白为原料,通过米曲霉的发酵生产大豆多肽,先以水解度为指标初步探索发酵工艺条件,然后通过正交试验,并以大豆多肽含量为指标确定摇瓶发酵的最佳工艺条件,即发酵液初始pH6.0,发酵培养温度28℃,培养基中大豆分离蛋白含量3%,摇瓶转速180r/min,发酵时间60h～70h,得到的大豆多肽发酵液具有良好的口感。     

超声波催化米曲霉发酵酱油的研究

超声波催化米曲霉发酵生产酱油的应用研究表明：在４０ＫＨｚ、１０Ｗ 的超声波作用下,酱油发酵速度是传统工艺的１５０％ ,米曲霉孢子生长率增加３－０％ ,孢子发芽率增加８％ 。通过显微镜观察,该超声波作用下的米曲霉细胞基本不受破碎。     

米曲霉产大豆异黄酮糖苷酶发酵条件的研究

通过单因素实验和正交实验，探讨米曲霉O3产大豆异黄酮糖苷酶的最佳条件。结果表明：在培养基组分为玉米芯3％、豆饼粉0．2％、KH2PO40．4％、CaCI20．04％、MgSO4-7H2O 0．04％，自然pH，接种量为10％，培养温度为30℃，60h的条件下，米曲霉O3菌株的产酶活性较高，可达388．572U／mL。     

低盐固态工艺条件下米曲霉3.042和米曲霉RIB40酿造酱油发酵性能的比较

探讨了在低盐固态酱油酿造工艺下,我国广泛应用的米曲霉3.042和日本的米曲霉RIB40在发酵性能方面的差异。对比了两株米曲霉种曲孢子数、大曲制备工艺、发酵过程中理化指标、有机酸含量以及酱油风味物质方面的不同。研究发现米曲霉3.042具有产孢快、生长迅速的特点。通过跟踪测定蛋白酶活、纤维素酶活和糖化酶活,确定了两株米曲霉的最佳收曲时间均为36h。同时发现米曲霉RIB40的糖化酶活很高(3208.939U/g干基,36h)。理化指标的变化情况表明:采用两株米曲霉制曲酿造酱油均达到了特级酱油标准。在有机酸方面,米曲霉RIB40酱醅的乳酸和乙酸的含量具有一定优势,这有利于酱油良好口感的形成。风味物质的检测结果表明:米曲霉RIB40酿造酱油中醇类物质具有优势,而米曲霉3.042在酯类物质方面具有优势。在实际生产中,可以根据产品需要选择合适的菌株。     

米曲霉产氨基酰化酶最佳活力条件的研究

通过在不同的反应时间,反应温度,缓冲液种类及pH条件下测定氨基酰化酶的活力,得出氨基酰化酶的最佳活力条件。试验结果表明,氨基酰化酶在反应温度为37℃、磷酸缓冲液pH为7．5、与底物反应30min时,活力最高。     

马铃薯渣发酵生产活性蛋白饲料的研究

以马铃薯渣为原料,选用啤酒酵母、面包酵母和黑曲霉为出发菌种,探究原料灭菌与不灭菌、菌种配伍及其比例对固态发酵产品中真蛋白含量、酸性蛋白酶活和纤维素酶活的影响。结果表明:发酵原料不灭菌处理条件下,菌种配伍以黑曲霉和啤酒酵母组合最佳,且比例为1∶1时,发酵完成后发酵产品中真蛋白含量最高,可达17.87%,较未发酵前提高171.17%;酸性蛋白酶活和纤维素酶活可达1187.93 U/g和61.77 U/g,可见利用马铃薯渣制备一定生物活性的蛋白饲料是可行的。      

马铃薯奶饮料生产工艺的研究

采用正交试验对马铃薯奶饮料的生产工艺及最佳工艺条件进行了研究。结果表明：马铃薯经去皮、预煮、破碎后,加５倍水,在９０℃下糊化４８ｍｉｎ,再加入０．３％的混合稳定剂（０．１％琼脂、０．１％黄析胶、０．１％ＣＭＣ－Ｎａ）,５％的脱脂牛奶,８％的白砂糖调配,然后装灌、密封,在１２１℃下杀菌２０ｍｉｎ,便可获得营养价值高、口感好,价格人氏廉的马铃薯奶饮料。     

皮状丝孢酵母产油脂的研究

本文对皮状丝孢酵母的生长发育和油脂合成进行了研究,监测和分析了酵母菌生长发育、油脂合成和脂肪酸成分及数量,检测了形态、OD值、糖氮代谢、p H、生物量、油脂含量和脂肪酸组分。结果表明:皮状丝孢酵母生长80 h左右时镜检测得菌细胞体内含油脂情况与80 h左右时实际提油获得的油脂量相一致,其油脂产量为3.66 g/L,含油率约为39.20%。皮状丝孢酵母生长0~6 h为适应期,此时糖氮的消耗明显,细胞数量缓慢增加;6~25 h为对数期,氮消耗非常显著,细胞数量急剧增加,细胞变大;25~120 h为稳定期,糖的消耗明显,消耗速度显然大于氮的消耗,细胞内开始慢慢积累油脂;之后为衰退期,氮的消耗基本趋于平稳。皮状丝孢酵母所产脂肪酸主要以C16、C18为主,此类脂肪酸适于进行脂交换制备生物柴油。      

甜菜创新胚珠纯系对比试验产质量分析

试验分析了两个二倍体、五个四倍体创新胚珠纯系的产质量与对照的差异。结果表明：94309—4（4n、处理3）是一个兼备高产、高糖性状的优异四倍体创新胚珠纯系,是培育高产、高糖新品种的优异品种资源。     

黑曲霉产菊粉酶的条件及其酶学性质的研究

对黑曲霉SL-09在摇瓶条件下产菊粉酶的奈件及其酶学性质进行了研究。结果发现,接种量和装瓶量对产酶影响不大,而pH值影响较为显著,最佳产酶pH值为6．0;在对催化条件的研究中发现最佳反应温度、底物浓度和pH值分别为60℃、60g/L和6．0;锰离子对酶活有较强的激活作用,最适浓度为1．5×10mol／L;同时发现该酶存在着严重的产物抑制现象,当果糖浓度大于1％时,菊粉酶活力将大幅度下降。     

Effects of silage protein degradability and fermentation acids on metabolizable protein concentration: A meta-analysis of dairy cow production experiments

A meta-analysis was conducted using data from dairy cow production studies to evaluate silage metabolizable protein (MP) concentrations. The data consisted of 397 treatment means in 130 comparisons, in which the effects of silage factors (e.g., date of harvest, wilting, silage additives) were investigated. Within a comparison, a fixed amount of the same concentrate was fed. A prerequisite of data to be included in the analysis was that silage dry matter (DM), crude protein (CP), ammonia N, lactic acid (LA), and total acid (TA) concentrations and digestibility were determined. A smaller data set (n = 248) comprised studies in which silage water-soluble N concentration was also analyzed. The supply of MP was estimated as amino acids absorbed from the small intestine using a model with constant values for ruminal effective protein degradability (EPD) and intestinal digestibility of rumen undegraded protein. Microbial protein was calculated on the basis of digestible carbohydrates and rumen degradable protein (RDP). Alternative models were used to estimate microbial protein formation, assuming the energy values of RDP and TA to be equivalent to 1.00, 0.75, 0.50, 0.25, and 0 times that of digestible carbohydrates. Because EPD values are seldom determined in production trials, they were derived using empirical models that estimate them from other feed components. The goodness of fit of models was compared on the basis of root mean squared error (RMSE) of milk protein yield (MPY) predicted from MP supply (adjusted for random study effect) and Akaike's information criterion. Metabolizable protein supply calculated from basal assumptions predicted MPY precisely within a study (RMSE = 16.2 g/d). Variable contribution of RDP to the energy supply for microbial synthesis influenced the precision of MPY prediction very little, but RMSE for MPY increased markedly when the energy supply of rumen microbes was corrected for TA concentration. Using predicted rather than constant EPD values also increased RMSE of MPY prediction. These observations do not mean that the supply of MP from undegraded feed protein is constant. However, it suggests that our current methods overestimate the range in EPD values and that the techniques have so many inherent technical problems that they can mask the true differences between the feeds. Including new elements in feed protein evaluation models may not improve the precision of production response predictions unless the consequent effects on the supply of other nutrients are taken into account.     

Effects of silage soluble nitrogen components on metabolizable protein concentration: a meta-analysis of dairy cow production experiments

A meta-analysis based on 253 treatment means from 80 dairy cow production experiments was conducted to estimate the effects of the silage water-soluble N components on milk production, milk urea N concentration, and the efficiency of N utilization in milk production. The original experiments were conducted to study forage treatments (e.g., digestibility, fermentation quality, or wilting). Both the level and composition of concentrates were fixed within an experiment. Silage soluble N (g/kg of N) was divided into ammonia N and soluble nonammonia N, which was determined without the use of protein precipitants; that is, soluble nonammonia N as defined here encompassed proteins, peptides, and free AA. Metabolizable protein was calculated as AA absorbed from the small intestine by using constant values for ruminal protein degradability and intestinal digestibility of undegraded protein. Metabolizable energy and protein intakes were used as independent variables in regression models investigating the effects of soluble N components on energy-corrected milk and milk protein yields. A mixed regression model was used to account for between-experiment variations; that is, the response of fixed factors was studied within experiments. Silage soluble N components did not affect the energy-corrected milk yield when used in bivariate models with metabolizable energy intake. Solubility of silage N had a negative effect on milk protein yield when included in the model with metabolizable protein. However, this effect was almost completely related to ammonia N, whereas the effect of soluble nonammonia N was nonsignificant and negligible. The effects of soluble N components on milk urea N concentration and efficiency of N utilization in milk production were consistent with milk production responses. A lack of milk production responses to silage soluble nonammonia N suggested that the partition of silage N into soluble and insoluble N (excluding ammonia N) did not markedly influence silage metabolizable protein concentration. Analysis of silage N solubility has limited value in practical feed evaluation, and silage metabolizable protein concentration can be estimated with reasonable accuracy by using constant values for ruminal protein degradability and intestinal digestion of undegraded feed protein.     

The effects of high-sugar ryegrass/red clover silage diets on intake,production, digestibility,and N utilization in dairy cows,as measured in vivo and predicted by the NorFor model

Grass silage-based diets often result in poor nitrogen utilization when fed to dairy cows. Perennial ryegrass cultivars with high concentrations of water-soluble carbohydrates (WSC) have proven potential for correcting this imbalance when fed fresh, and have also been shown to increase feed intake, milk production, and N utilization. The possibility of achieving corresponding effects with silage-based diets was investigated in change-over experiments in an incomplete block design with 16 (yr 1) or 12 (yr 2) Swedish Red dairy cows in mid lactation. Measurements on N excretion and rumen parameters were performed on subgroups of 8 and 4 cows, respectively. In yr 1, 2 ryegrass cultivars (standard = Fennema; high-WSC = Aberdart) and 2 cuts (first and second) were compared. In all treatments, ryegrass silage was mixed 75/25 on a dry matter (DM) basis, with red clover silage before feeding out. In yr 2, 1 basic mixture from the different cuts of these 2 cultivars was used and experimental factors were red clover silage inclusion (25 or 50%) and sucrose addition (0 or 10%) on a silage DM basis. Differences in WSC concentration in the silage mixtures in yr 1 were minor, whereas the differences between cuts were more substantial: 100 compared with 111 g/kg of DM for first-cut silage and 39 compared with 47 g/kg of DM for second-cut silage. The silages fed in yr 2 had a WSC concentration of 115 or 102 g/kg of DM (25 or 50% red clover, respectively), but when sucrose was added WSC concentration reached 198 and 189 g/kg of DM, respectively. Milk production (kg/d) did not differ between treatments in either year. Red clover inclusion to 50% of silage DM increased milk protein. Nitrogen efficiency (milk N/feed N) increased from 0.231 to 0.254 with sucrose inclusion in yr 2 (average for the 2 red clover levels). Overall rumen pH was 5.99 and increased sucrose level did not affect pH level or daily pH pattern. Sucrose addition reduced neutral detergent fiber digestibility, particularly at higher inclusion rates of clover. Rumen pool of total purines did not differ between treatments, nor did protein production assessed from urinary allantoin. The NorFor feed evaluation model overestimated digestibility of neutral detergent fiber and N, but underestimated N excretion in feces. We concluded that addition of WSC to dairy cow diets at levels up to 3 kg of WSC per day (>14% of DM) does not dramatically affect cow performance.     

Effect of supplementing rumen-protected methionine on production and nitrogen excretion in lactating dairy cows

Two 4 × 4 Latin square trials (4-wk periods; 16 wk total) were conducted to see whether supplementing rumen-protected Met (RPM; fed as Mepron) would allow feeding less crude protein (CP), thereby reducing urinary N excretion, but without losing production. In trial 1, 24 Holsteins were fed 4 diets as total mixed rations containing [dry matter (DM) basis]: 18.6% CP and 0 g of RPM/d; 17.3% CP and 5 g of RPM/d; 16.1% CP and 10 g of RPM/d; or 14.8% CP and 15 g of RPM/d. Dietary CP was reduced by replacing soybean meal with high-moisture shelled corn. All diets contained 21% alfalfa silage, 28% corn silage, 4.5% roasted soybeans, 5.8% soyhulls, 0.6% sodium bicarbonate, 0.5% vitamins and minerals, and 27% neutral detergent fiber. There was no effect of diet on intake, weight gain, or yields of protein, lactose, and solids-not-fat. However, production was greater at 17.3% CP plus RPM and 16.1% CP plus RPM than on the other 2 diets. Apparent N efficiency (milk N:N intake) was greatest on the lowest CP diet containing the most RPM. Linear reductions in milk urea N and urinary N excretion were observed with lower dietary CP. In trial 2, 32 Holsteins were fed 4 diets as total mixed rations, formulated from ingredients used in trial 1 and containing 16.1 or 17.3% CP with 0 or 10 g of RPM/d. On average, cows were calculated to be in negative N balance on all diets because of lower than expected DM intake. There was no effect of RPM supplementation on any production trait. However, higher CP gave small increases in yields of milk, protein, and solids-not-fat and tended to increase DM intake and lactose yield. Apparent N efficiency was greater, and milk urea nitrogen was lower, on 16.1% CP. In trial 1, feeding lower CP diets supplemented with RPM resulted in improved N efficiency and reduced urinary N excretion. However, in trial 2, reducing dietary CP from 17.3 to 16.1% reduced milk secretion, an effect that was not reversed by RPM supplementation at low DM intakes when cows were apparently mobilizing body protein.     

Effect of goat milk composition on cheesemaking traits and daily cheese production

Cheese yield is strongly influenced by the composition of milk, especially fat and protein contents, and by the efficiency of the recovery of each milk component in the curd. The real effect of milk composition on cheesemaking ability of goat milk is still unknown. The aims of this study were to quantify the effects of milk composition; namely, fat, protein, and casein contents, on milk nutrient recovery in the curd, cheese yield, and average daily yield. Individual milk samples were collected from 560 goats of 6 different breeds. Each sample was analyzed in duplicate using the 9-laboratory milk cheesemaking assessment, a laboratory method that mimicked cheesemaking procedures, with milk heating, rennet addition, coagulation, curd cutting, and draining. Data were submitted to statistical analysis; results showed that the increase of milk fat content was associated with a large improvement of cheese yield because of the higher recovery of all milk nutrients in the curd, and thus a higher individual daily cheese yield. The increase of milk protein content affected the recovery of fat, total solids, and energy in the curd. Casein number, calculated as casein-to-protein ratio, did not affect protein recovery but strongly influenced the recovery of fat, showing a curvilinear pattern and the most favorable data for the intermediate values of casein number. In conclusion, increased fat and protein contents in the milk had an effect on cheese yield not only for the greater quantity of nutrients available but also for the improved efficiency of the recovery in the curd of all nutrients. These results are useful to improve knowledge on cheesemaking processes in the caprine dairy industry.