球形节杆菌C224分批发酵2-酮基-D-葡萄糖酸的条件优化及其动力学模型的构建

通过优化发酵条件,提高球形节杆菌C224菌株利用大米淀粉水解糖分批发酵2-酮基-D-葡萄糖酸的生产强度,并在此基础上构建其发酵动力学模型。在50 L的发酵罐上考察了通气量与葡萄糖浓度对2-酮基-D-葡萄糖酸发酵的影响,并基于Logistic方程、Luedeking-Piret方程和物料平衡计算分别构建了菌体生长、产物形成和底物消耗的动力学模型。研究结果表明,通气量低于1.5 v.v-1.m-1时,发酵生产强度明显减小,糖酸转化率有所降低;发酵培养基中的葡萄糖浓度以120.0～180.0 g/L为宜,过高或过低对生产强度和糖酸转化率均有不利影响。在适宜的发酵条件下,球形节杆菌C224菌株分批发酵生产2-酮基-D-葡萄糖酸的生产强度达6.36～6.54 g/(L.h),糖酸转化率为0.96～0.97 g/g。所构建动力学模型的计算值与实验值拟合效果良好,各项模型的相关系数R2均大于0.95,说明其能够揭示球形节杆菌C224分批发酵2-酮基-D-葡萄糖酸代谢基本特征。     

Effect of spray drying and freeze drying on the immunomodulatory activity,bitter taste and hygroscopicity of hydrolysate derived from whey protein concentrate

The main aim of the present work was to obtain microencapsulated whey protein concentrate hydrolysate (WPCH) in order to reduce its bitter taste and resistance to hygroscopicity without impairing its immunoregulatory activity by spray drying or freeze drying with whey protein concentrate (WPC) and sodium alginate (SA) as carriers. To attenuate its bitter taste, the WPCH were encapsulated with WPC or the mixture of WPC and sodium alginate (WPC/SA). The splenocyte proliferation activity, hygroscopicity, bitter taste and morphology of non-encapsulated WPCH and encapsulated WPCH were evaluated. Results revealed that WPCH could significantly enhance splenocyte proliferation activity compared with WPC itself. Both spray drying and freeze drying with or without carrier material addition did not exert negative effect on the immunomodulatory activity of WPCH. The bitterness, determined by taste dilution analysis method, of both WPC-encapsulated WPCH and WPC/SA-encapsulated WPCH was significantly lower than that of the original non-encapsulated WPCH. Morphological analysis showed that freeze drying process could not encapsule WPCH as spray drying did. All of these indicated that spray drying with WPC or the mixture of WPC and SA (WPC/SA) as carriers was beneficial for reducing the bitter taste and hygroscopicity without impairing the immunoregulatory activity of whey protein hydrolysate.     

Effects of intramammary infusions of casein hydrolysate,ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid,and lactose at drying-off on mammary gland involution

The transition from the lactation to the dry period in dairy cows is a period of high risk for acquiring new intramammary infections. This risk is reduced when involution of mammary glands is completed. Consequently, strategies that accelerate the involution process after drying-off could reduce the incidence of mastitis. The objective of this study was to assess the effect of 3 different treatments on mammary gland involution. Each quarter of 8 Holstein cows in late lactation was randomly assigned at drying-off to an intramammary infusion of casein hydrolysate (CNH; 70 mg), ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA; 5.7 g), lactose (5.1 g), or saline 0.9% (control) solutions. Milk samples were collected on the last 2 d before and 1, 3, 5, 7, 10, and 14 d after the last milking for determining concentrations of mammary gland involution markers. Lactoferrin, somatic cell counts (SCC), BSA, and Na⁺ concentrations, as well as matrix metalloproteinase-2 and matrix metalloproteinase-9 activities gradually increased in mammary secretions during the first 2 wk following the last milking, whereas milk citrate and K⁺ concentrations decreased. As involution advanced, the Na⁺:K⁺ ratio increased, whereas the citrate:lactoferrin ratio decreased. Compared with mammary secretions from control quarters, mammary secretions of quarters infused with CNH had higher SCC on d 1, 3, 5, and 7, and greater BSA concentrations on d 1, 3, and 5. Similarly, the CNH treatment induced a faster increase in lactoferrin concentrations, which were greater than in milk from control quarters on d 3, 5, and 7 after drying-off. Milk citrate concentrations were unaffected by CNH but the citrate:lactoferrin ratio was lower in CNH-treated quarters on d 3 and 5 than in control quarters. Moreover, CNH treatment hastened the increase in Na⁺ concentration and in the Na⁺:K⁺ ratio on d 1. Infusion of CNH also led to an increase in proteolytic activities, with greater matrix metalloproteinase 9 activities on d 1 and 3. The EGTA infusion increased SCC above that of control quarters on d 1 and 3 but it had no effect on the other parameters. Lactose infusion had no effect on any of the involution markers. In this study, intramammary infusions of CNH were the most efficient treatment to accelerate mammary gland involution, suggesting a potential role of CNH as a local milk secretion inhibitor during milk stasis.     

鱼精蛋白-一种新型食品防腐剂

鱼精蛋白是存在于各类动物精巢组织中的一种多聚阳离子肽,是一种高效、安全、值得开发的新型天然食品防腐剂。本文综述了鱼精蛋白的来源、组成、提取、纯化、防腐性能、防腐机理以及其防腐应用。     

Antioxidant and nitric oxide inhibitory activities of tilapia (Oreochromis niloticus) protein hydrolysate: effect of ultrasonic pretreatment and ultrasonic‐assisted enzymatic hydrolysis

Ultrasound was incorporated to processing of fish protein hydrolysate to facilitate homogenate pretreatment and enzymatic hydrolysis of tilapia (Oreochromis niloticus) muscle protein. Their effects on Flavourzyme hydrolysis and biological activities of the tilapia hydrolysate were examined. The ultrasound‐assisted hydrolysis caused reduction in degree of hydrolysis ranging from 23% to 35% relative to that of the conventional process. The 70 W ultrasound‐assisted hydrolysis process increased DPPH radical‐scavenging activity and reducing power of tilapia hydrolysate prepared from the non‐pretreatment homogenate by 33% and 45%, respectively. All hydrolysates have no cytotoxicity on RAW264.7 cell lines at the maximum concentration of 20 mg protein mL^?1. The 70 W ultrasound pretreatment at 30 and 45 min combined with conventional hydrolysis is the suitable condition for producing tilapia hydrolysate with nitric oxide inhibitory and antioxidative activities on RAW264.7 cell lines, respectively. As a result, ultrasound could be applied to enzymatic protein hydrolysis either as pretreatment or during the hydrolysis.     

改性对玉米蛋白质功能性质和结构的影响—（Ⅲ）复合改性

改性是加强食品蛋白质功能性质的有效方法,复合改性是现代食品蛋白质化学的热点研究,通过琥珀酰化对3%水解度玉米蛋白质水解物的改性发现,随酰程度的增大,玉米蛋白质水解物的分子柔性,表面疏水性和溶性粘度不断增大,这一方面表明3%水解度的玉米蛋白质水解仍具有部分蛋白质高级结构,另一方面表明琥珀酰化改变了玉米蛋白质水解物的结构,而随着琥珀酰化程度的增大,玉米蛋白质水解物的乳化活性和乳化稳定性得到加强,这表明复合改性明显得优于单一改性。     

Collagenous hydrolysates from untraditional sources of proteins

Synopsis Sufficiently pure collagenous hydrolysates, suitable for application in skin and hair care cosmetics, have been prepared through biotechnological methods with the use of commercially available enzymatic preparations from short cattle tendons (musculus extensor communis, musculus flexor digitorum, musculus flexor digitorum profundis). These hydrolysates contain neither lipoid nor aminosaccharide components, content of primary amino groups reaches around 1.1 mmol g⁻¹ and the average molecular weight of the resulting collagenous hydrolysates does not exceed 2000 g mol⁻¹ (2.0 kDa). Short cattle tendons represent a relatively pure and easily available source of collagens and are, despite their generally known low nutritional value, used only as a feeding mixture component.     

A partially degraded product of phytate suppresses the proliferation of HCT116 colorectal cancer cells

Phytate, myo-inositol hexaphosphate (IP6), has been shown to possess anti-carcinogenic qualities. IP6 appears to be partially digested in the digestive tract and degraded into inositol di, tri-, and tetra-phosphate (IP2, IP3, and IP4). The present study investigated whether IP3-rich phytate hydrolysate (IP3-RPH), a partially degraded product from phytate, plays a role in the suppression of cell proliferation, using an HCT116 colon carcinoma cell line. IP3-RPH suppresses cell proliferation as does IP6, and the suppression activity of IP3-RPH is higher than that of IP6. Suppression modes clearly differed between IP3-RPH and IP6. Our findings suggest that partially degraded IP6 products are responsible for the suppression of colon carcinogenesis by IP6.     

Purification and characterisation of a novel antioxidant peptide from porcine haemoglobin hydrolysate

Porcine haemoglobin, which is normally discarded as a by‐product of meat industry, was hydrolysed using pepsin, AS1398 neutrase, trypsin, flavorzyme, papain and alcalase respectively. The peptic hydrolysate exhibited the highest antioxidant activities than those of other hydrolysates, which was separated using ultrafiltration membranes, and consecutively using chromatographic methods including ion‐exchange chromatography on SP Sephadex C‐25 column, gel filtration chromatography on Sephadex G‐25 column and reversed‐phase high performance liquid chromatography. Finally, a novel antioxidant peptide from porcine haemoglobin (APPH) was purified, and its sequence was identified to be ARRLGHDFNPDVQAA (1666 Da) using mass spectrometry. APPH exhibited significant higher lipid peroxidation inhibitory ability than that of α‐tocopherol as positive control (P < 0.05), and efficiently quenched hydroxyl radical (IC₅₀ = 26.9 μm ). APPH agrees with the 115–129 residues of the β‐chain from porcine haemoglobin. These results indicate that APPH would be a beneficial ingredient for functional food and pharmaceuticals.     

玉米蛋白加工利用研究进展

在湿法玉米淀粉加工中,玉米蛋白存在于副产物玉米黄粉、玉米胚芽饼和玉米浆中。文章在分析玉米蛋白氨基酸组成等特性的基础上,综合分析玉米蛋白加工利用现状和玉米蛋白水解物的功能特性,指出玉米蛋白水解物在食品工业上应用的潜力。