牦牛“曲拉”精制干酪素工艺研究

由传统牦牛“曲拉”制得的干酪素品质不佳的主要原因是脂肪氧化、杂质过高，该文用改良的工艺流程，通过L₉(3⁴)正交试验，研究酶制剂和离心条件对“曲拉”所制干酪素品质的影响。结果表明：酶制剂最佳应用条件为料液温度38℃，pH值4.2，胰蛋白酶浓度1.0 g/kg(处理时间5 min)，脂肪酶浓度0.01 g/kg，乳糖酶浓度0.03 g/kg；最佳离心工艺参数为，转速16000 r/min、时间10 min、温度50℃。高速离心法和酶处理过程，既能除去料液中脂肪、乳糖、尘埃等杂质，又使制品溶解黏度、色泽、气味等明显改善。红外光谱检测，制品质量优于传统产品。     

Canine Pancreatic‐Specific Lipase Concentrations in Dogs with Heart Failure and Chronic Mitral Valvular Insufficiency

Background

Chronic mitral valvular insufficiency (CMVI) in dogs is very common and might cause clinical signs of congestion and poor tissue perfusion.

Hypothesis

Poor tissue perfusion from CMVI causes pancreatitis in dogs, as indicated by serum pancreatic lipase concentrations.

Animals

Sixty‐two client‐owned dogs consisting of 40 dogs with different stages of heart failure from CMVI and 22 age‐matched healthy dogs, based on full cardiac exam and routine laboratory tests.

Methods

Prospective, controlled, observational study. Serum canine pancreatic lipase immunoreactivity (cPLI) concentrations were determined by quantitative cPLI test in healthy and CMVI groups.

Results

Serum cPLI concentrations were 54.0 μg/L (IQR: 38.0–78.8 μg/L) in control, 55.0 μg/L (IQR: 38.3–88.8 μg/L) in ISACHC I, 115.0 μg/L (IQR: 45.0–179.0 μg/L) in ISACHC II and 223.0 μg/L (IQR: 119.5–817.5 μg/L) in ISACHC III. Close correlation to serum cPLI concentration was found in the left atrial to aorta (LA/Ao) ratio (r = 0.597; P = .000) and the severity of heart failure (r = 0.530; P = .000).

Conclusions and Clinical Importance

This study found CMVI is associated with pancreatic injury in congestive heart failure caused by CMVI. Therefore, periodic monitoring on cPLI could be useful in monitoring dogs in heart failure.     

微生物脂肪酶概况及其动物营养效应的研究进展

微生物脂肪酶是工业用脂肪酶的重要来源,是生物技术和有机化学应用中广泛使用的酶类之一。文章从微生物脂肪酶来源、酶学特性、在动物消化道中的营养效应和作用机理方面进行综述,主要介绍国内外关于脂肪酶应用在动物饲料方面所取得的一些研究成果,为微生物脂肪酶在饲料中的开发与应用提供参考。     

Direct lipase-catalyzed lipophilization of chlorogenic acid from coffee pulp in supercritical carbon dioxide

The direct esterification of chlorogenic acid (5-CGA) by immobilized Candida antarctica lipase B (Novozym 435) in supercritical CO₂/t-butanol has been studied. The Taguchi approach was applied to evaluate the effects of temperature (35–55 °C), pressure (150–250 bar), t-butanol (2–10%, v/v), and the enzyme amount (10–30 mg/ml), on the ester concentration and overall conversion. Optimum reaction conditions were established at: 150 bar, 55 °C, 10% t-butanol (v/v), 20 mg/ml of lipase. Addition of 20 mg/ml of molecular sieves (3 Å) was also necessary to minimize the inhibiting effect of the increasing water concentration. Maximum conversions reached 77, 82 and 85% in 25 h using geraniol, pentanol and heptanol as aliphatic chain donors, respectively. HPLC analysis demonstrated the selective esterification of 5-CGA from a coffee pulp aqueous-methanolic extract, which reached a conversion to heptyl ester of 65% at the optimal condition. The supercritical CO₂ selectivity towards the esterified product was the working principle of this study, by which minimized interphase transport limitations and enhanced mass-transfer phenomena substantially improved the reaction kinetics.     

Analytical validation of an ELISA for measurement of canine pancreas‐specific lipase

Background: The diagnosis of canine pancreatitis is challenging. Clinical presentation often includes nonspecific clinical signs, such as vomiting, anorexia, and abdominal discomfort. Increased serum lipase activity can be indicative of pancreatitis; however, it can also be increased with other conditions. An immunoassay for measurement of canine pancreas‐specific lipase in canine serum that would be suitable for commercial application and provide rapid results would be beneficial. Objective: The goal of this study was to validate the Spec cPL assay, a commercially available ELISA for the quantitative measurement of canine pancreas‐specific lipase. Methods: Dynamic range, dilutional linearity, precision, interfering substances, assay stability, and reproducibility were investigated for analytical validation. The method was compared with the reference assay, canine pancreatic lipase immunoreactivity (cPLI), and included evaluation of a sample population of dogs and bias. Results: Analytical validation showed a dynamic range of 36–954 μg/L; good precision (intra‐ and interassay coefficient of variation <12%); absence of interference from lipid, hemoglobin, or bilirubin; 12‐month kit stability; and good reproducibility. Method comparison showed a positive bias relative to the cPLI reference method; however, the bias can be accommodated by adjustment of decision limits. The upper limit of the reference interval for Spec cPL was determined to be 216 μg/L based on the upper 97.5th percentile of results from 93 clinically healthy, kennel‐housed dogs. Conclusions: Validation data demonstrated that the Spec cPL assay provides reproducible results for canine pancreas‐specific lipase. A readily available assay for measurement of this enzyme allows broader clinical utilization of this analytical tool, generating timely results to aid in the diagnosis of canine pancreatitis.     

原料乳中嗜冷菌种类及嗜冷芽孢杆菌研究进展

嗜冷菌能在原料乳冷藏条件下生长,其分泌蛋白酶和脂肪酶降解牛乳中的蛋白和脂肪,导致牛乳变质。本文归纳了原料乳中嗜冷菌的种类,总结嗜冷芽孢杆菌的危害研究进展,重点包括嗜冷菌常见种型、危害特点、分泌的蛋白酶和脂肪酶。最后探讨了嗜冷芽孢杆菌的研究方向。     

气调密闭贮藏对芝麻品质的影响

芝麻营养和药用价值高,应用潜力巨大,但贮藏稳定性差。为找到一种绿色、经济的芝麻贮藏方式,利用充CO_2、充N_2、抽真空、密封等方式分析了不同气调密闭贮藏方式下芝麻的水分、粗蛋白、粗脂肪、过氧化值、酸价、脂肪酶活性、脂肪氧化酶活性、脂肪酸等理化指标的变化,探究了不同气调密闭贮藏方式对芝麻品质的影响规律。结果表明:气调密闭贮藏能有效延缓芝麻的氧化酸败,尤其是充CO_2或充N_2气调密闭贮藏可显著降低芝麻贮藏过程中酸价和过氧化值的增加幅度,减轻脂肪的氧化酸败,基本保持原有品质。     

Production of Lipase Using Cassava Peel and Sunflower Oil in Solid-State Fermentation： Preliminary Study

Full use of residues from industrial processes is a fundamental necessity of contemporary society, since it avoids impacts to the environment by using residues as inputs for other products of high economic and social importance. In this study, lipase production of the crude enzymatic extracts obtained by Aspergillus niger using cassava peel as substrate and sunflower oil as an inductor was investigated. The optimized cultivation temperature and concentration of inductor were determined using the response surface methodology. The two variables studied exercised influence in the production of lipase in the 95% level of confidence. The response surface obtained indicated that the conditions that maximize lipase activity production were 30.5 ~C and initial concentration of sunflower oil was 2.5% （w/w）. Through this analysis, it is evident that extremes in temperature and concentration of inductor tend to decrease lipase production, since low temperatures decrease metabolism and high temperatures may inactivate the lipase. Optimum lipase yield was 59.8 U/g of dry peel which was fermented for 60 h. Lipase production presents a peak of 61.3 U/g, at 72 h of fermentation. However, this value is statistically equal （p 〉 0.05） of the value of lipase activity obtained for 60 h and 84 h of fermentation.     

荷叶中生物碱的分离纯化及脂肪酶活性抑制作用研究

荷叶中含有生物碱等多种有效成份,同时具有药食两用的功效.本文研究了荷叶提取物的分离和纯化条件与荷叶乙醇提取物对脂肪酶活性的抑制作用,发现荷叶中各生物碱的含量为0.1～0.6%,经大孔树脂预纯化后,生物碱的含量提高近100倍.当流动相中三乙胺含量增加至0.2%时,峰形明显改善,各色谱峰重叠部分小,高纯度收集部分加宽;1 mg/ml荷叶提取物对脂肪酶的抑制作用为11.25%,荷叶碱的抑制活性为25.77%,N-降荷叶碱的抑制活性为21.37%,O-降荷叶碱的抑制活性为24.63%.     

粗状假丝酵母产酶能力及发酵条件的优化

对一株产脂肪酶粗状假丝酵母(ACCC20231)产酶特性进行了研究.结果表明,在培养基初始pH值6.0、30℃下培养31 h该菌出现最高酶活.对其发酵培养基成分进行优化,确定最适培养基组成为麦芽粉2%,蛋白胨1%,(NH4)2SO4 0.1%,MgSO4 0.5%,以1%棉子油作为诱导剂,优化后该菌株产酶能力明显提高,达6.2 U·mL-1.