从萌发的油菜种子中制备脂肪酶

测定不同萌发期油菜幼苗的脂肪酶活性,采用“盐析→超滤→M-Bondapak-C18 柱层析”的工艺路线,建立一种简单且高效的油菜脂肪酶纯化方法。结果表明：通过测定不同培养时间的油菜幼苗的脂肪酶比活力,发现培养6d 的油菜幼苗脂肪酶比活力最高,此时期的油菜幼苗适合作为脂肪酶提取的材料;对脂肪酶比活力为1.89U/mg的油菜蛋白粗提物采用盐析法沉淀脂肪酶时,得到脂肪酶的比活力为2.07U/mg,回收率为82.47%;采用截留分子质量为10000D 的超滤膜对脂肪酶盐析物进行脱盐和除去小分子杂蛋白处理,得到的脂肪酶的比活力为2.46U/mg,回收率为75.84%;进一步采用M-Bondapak-C₁₈ 柱层析纯化超滤液,脂肪酶最高比活力为9.14U/mg,回收率为34.13%。所得到的脂肪酶的活性达到了商品化脂肪酶的水平。     

萌芽时间、温度以及不同浸泡液对萌芽豇豆γ-氨基丁酸含量的影响

γ-氨基丁酸(GABA)是一种功能性成分,在食品中有着广阔的利用前景。该实验以豇豆为原料,研究了发芽温度和时间对豇豆发芽率和GABA含量的影响,同时分析了不同浸泡液对萌芽豇豆中GABA含量的影响。结果表明:在20～30℃下萌发24h,豇豆发芽率高且出芽整齐。在30℃下,萌发24h的豇豆GABA含量高达815.21μg/g,较萌发前高158.32μg/g。在浸泡液pH为4时,萌芽豇豆GABA含量可达2330.90μg/g,为萌发前豇豆GABA含量的4倍左右。Ca2+浓度在0.1mmol/L时,GABA含量可高达886.24μg/g,继续增加Ca2+浓度,则GABA含量降低。磷酸吡哆醛(PLP)浸泡液浓度在4mmol/L时,萌芽豇豆GABA的含量可达843.14μg/g,较萌发前提高了20%左右。VB6浸泡液在1mmol/L时,萌芽豇豆GABA含量为966.61μg/g,是萌芽前豇豆GABA含量的1.5倍左右。NaCl和L-谷氨酸浸泡液不能起到促进萌发豇豆富集GABA的作用。可见通过控制发芽时间和温度以及选择合适的浸泡液培养,能有效调节豇豆富集GABA。     

RECOGNITION OF TWO LIPASES FROM BARLEY AND GREEN MALT

Lipase was extracted from ground samples of germinating and ungerminated barley, using the detergent Triton X-100. Enzyme activity, measured by the release of oleic acid from radioactively labelled triolein, was approximately half that in suspensions of barley flour. Two distinct lipases, both active at neutral pHs, and having similar molecular weights (around 400,000) but differing in their ionic properties, were isolated from barley. The more abundant lipase was found mainly in the embryo, while the other was located in the endosperm. Both total and extractable lipase activity increased during germination.     

Biochemical changes and in-vitro protein digestibility of the endosperm of germinating dolichos lablab

A gradual decrease was noted in total protein, soluble protein and protein fractions such as albumin, globulin, prolamine andglutelin in the endosperm of Dolichos lablab L germinated for 8 days. Prolamine showed a maximum decrease of 85% whereas only a 25% decrease was noted in the globulin fraction. Both acid and alkaline protease activities increased during germination, and the acid protease activity was consistently higher than the alkaline protease activity throughout. Electrophoretic studies showed that high molecular weight polypeptide bands disappeared with the appearance of new low molecular weight polypeptide bands in the endosperm proteins of the germinating seeds. Total phenolics and tannin contents and trypsin inhibitory activity also increased during the progressive germination. Germination increased the in-vitro protein digestibility of the endosperm of Dolichos lablab in the presence of proteolytic enzymes like pepsin, trypsin and pancreatin. It showed a negative but non-significant correlation with trypsin inhibitory activity, phenolics and tannin contents. Amylase activity also increased gradually up to the sixth day of germination which coincided with the increase in the reducing sugars.     

Effect of pulsed electric field on the germination of barley seeds

This study explores metabolic responses of germinating barley seeds upon the application of pulsed electric fields (PEF). Malting barley seeds were steeped in aerated water for 24 h and PEF-treated at varying voltages (0 (control), 110, 160, 240, 320, 400 and 480 V). The seeds were then allowed to finish germination in saturated air. It is shown that exposure of germinating barley to PEF affects radicle emergence without significantly affecting the seeds’ gross metabolic activity, as quantified by isothermal calorimetry. An exploration of protein 2-DE profiles of both the embryo and the starchy endosperm showed that, at the studied time scale, no significant changes were found in proteins present at concentrations higher than the detection limit. However, western blotting demonstrated that α-amylase concentration decreases in the PEF-treated seeds.     

Changes in quantities of inositol phosphates during maturation and germination of legume seeds

 The changes in the quantities of inositol phosphates during the maturation and germination of pea, faba bean and lupin seeds were determined in two consecutive (1993 and 1994) years of differing weather conditions. Irrespective of the year, all seeds accumulated predominantly inositol hexaphosphate (IP₆). The weather conditions influenced the accumulation of inositol phosphates in maturing seeds, but they did not influence the total content. Gradual degradation of inositol phosphates occurred during seed germination. After 8 days of germination, IP₆ was degraded by some 80% in peas, 78% in faba beans and 42% in lupin seeds. The enzymic hydrolysis of higher forms of inositol phosphates (IP₆ and IP₅) in germinating seeds was assumed to yield inositol tetraphosphate (IP₄) and inositol triphosphate (IP₃), because the quantities of these compounds increased during seed germination. Received: 1 August 1997 / Revised version: 13 October 1997     

Biochemical changes in fermenting African locust bean (Parkia biglobosa) during 'iru' fermentation

The enzymic activities and biochemical changes in the principal food constituents of African locust bean were investigated. The reducing sugar level increased from 63 mg/g to 134 mg/g during the first 24 hr but subsequently decreased. Amylase activity was not detected. The lipase activities were detectable with the peak at 48 hr after the start of fermentation. The most significant activity during the fermentation is the rapid and steady increase in the quantity of free amino acids throughout the fermentation. This is due to a consistently active proteinase activity by the fermentative microorganisms. The number and quantities of each amino acids analysed also increased in the fermented beans. Glutamic acid, valine, aspartic acid and alanine were rapidly liberated during the fermentation. The changes observed are compared with the fermentation of other protein rich seeds.     

Changes in quantities of inositol phosphates during maturation and germination of legume seeds

 The changes in the quantities of inositol phosphates during the maturation and germination of pea, faba bean and lupin seeds were determined in two consecutive (1993 and 1994) years of differing weather conditions. Irrespective of the year, all seeds accumulated predominantly inositol hexaphosphate (IP₆). The weather conditions influenced the accumulation of inositol phosphates in maturing seeds, but they did not influence the total content. Gradual degradation of inositol phosphates occurred during seed germination. After 8 days of germination, IP₆ was degraded by some 80% in peas, 78% in faba beans and 42% in lupin seeds. The enzymic hydrolysis of higher forms of inositol phosphates (IP₆ and IP₅) in germinating seeds was assumed to yield inositol tetraphosphate (IP₄) and inositol triphosphate (IP₃), because the quantities of these compounds increased during seed germination. Received: 1 August 1997 / Revised version: 13 October 1997     

白肋烟种子萌发的生理生化动态研究

以TN86种子为材料,分析了白肋烟种子萌发特征及有关活性酶与相关物质的变化动态。结果表明,呼吸强度、淀粉酶与可溶性总糖和还原糖、蛋白酶与总游离氨基酸、脂肪酶与脂肪酸,以及过氧化物酶(POD)、多酚氧化酶(PPO)、可溶性蛋白质、脯氨酸(pro)、丙二醛(MDA)等的活性或含量都随萌发进程呈上升趋势,其间虽有所波动,但最高峰值期大都在第84-168h之间,仅POD与PPO活性和MDA含量在萌发中期才开始明显上升,直至萌发结束时达高峰值。淀粉酶、蛋白酶、脂肪酶活性与各自催化水解的产物含量呈极显著正相关;而粗脂肪含量随萌发进程而下降,与脂肪酸呈极显著负相关。萌发集中在48-72h,发芽势90%,同步指数0.92。萌发动态符合Logistic生长曲线方程。     

芝麻菜种子萌发过程中芽苗生长和硫苷代谢

目的:研究发芽过程中芝麻菜生长状况和硫苷代谢的变化情况,从而选出适宜食用的芝麻菜品种及其生长期。方法:以"板叶"和"东升"两个品种的芝麻菜种子为试材,发芽0、2、4、6和8 d后测定其芽长、株重、含水量、游离氨基酸含量、可溶性糖含量及硫苷代谢相关指标。结果:随着发芽时间的延长,两个品种芝麻菜芽苗的芽长、株重和含水率逐渐升高;"板叶"和"东升"中游离氨基酸含量均在第8 d最高,分别为7.68 μg/株和7.64 μg/株;可溶性糖含量均于第6 d达到最高,分别为216.8 μg/株和203.5 μg/株。总硫苷含量在发芽2 d达到最高,而发芽8 d后降至最低,分别为53.74 nmol/株和55.87 nmol/株;异硫氰酸盐形成量均在发芽4 d最高,分别达到66.82 nmol/株和89.76 nmol/株,而黒芥子酶则分别在第2 d和第4 d活性最高,发芽8 d后两者无显著差异。结论:发芽可以提高种子的品质,芽苗生长过程中,储藏性糖类物质的降解先于蛋白质,硫苷被不断降解,黑芥子酶活性和异硫氰酸盐的形成存在时空差异。综合来看,"东升"的植株大小、所含营养物质,GLs及ITCs含量较"板叶"更高,芽苗中主要关注的功能成分为ITCs,选用4 d为较合适的发芽时间。     

Studies on the relationship between antioxidative activity of rice hull and germination ability of rice seeds

An investigation of the germination potentials of seeds of Indica and Japonica rice varieties revealed that while the long-life rice seeds retained the germination ability even on storage for a year at 30°C, the germination ability of the short-life rice seeds tended to decrease when stored beyond 6 months. The role of rice hull constituents in the preservation of the germination property during ageing of rice seeds was investigated with special emphasis on rice antioxidants. Antioxidative assay with chloroform-methanol and methanol-water extracts of hull, bran-germ and grain fractions of two Indica and five Japonica rice varieties indicated that all of the seed varieties belonging to Indica and Japonica possessed a strong antioxidative activity in the hull fraction. Hull extracts of long-life rice seeds showed relatively higher activities than those of short-life rice seeds. In contrast, hull extracts of long-life rice seeds had higher inhibitory effects on lipoxygenase activity than did those of short-life varieties. Quantification of the natural antioxidants indicated that ^α-tocopherol in rice oil to be present in the range of 318.3–450.1 μg g^?1 oil while the amount of oryzanol in the hull, bran-germ and grain fractions of rice was found to be 1.0–5.8, 95.4–279.8 and 3.0–9.4 μg g^?1 sample respectively. The results, however, did not show any positive correlation between the amount of natural antioxidants in rice hull and germination potentials of rice seeds. The amount of total phenolic constituents in rice hull was found to range from 190–390 μg g^?1 sample, the levels being far higher in long-life rice seeds in comparison with the short-life rice seeds. These values seemed to agree well with the germination data of the corresponding rice variety. The investigation revealed a strong influence of the level of phenolic constituents in rice hull on the storability of rice seeds.     

Processing,suitability and nutritive value of field bean seeds after germination

An attempt was made to obtain hydrolysates from field bean seeds after germination. The activity of native proteolytic enzymes, ascorbic acid and phytate phosphorus contents, as well as the activity of proteolytic enzyme inhibitors were studied, as influenced by seed steeping, water acidity and aerating conditions. Germinated field bean seeds were found to be suitable for hydrolysate production. The enzyme activity, as well as the contents of compounds responsible for the nutritive value of seed was determined and depended on germinating conditions.     

Lipase production by lactic acid bacteria and activity on butter oil

Over 100 different lactic acid bacteria representing the genera,Lactobacillus, Lactococcus, Leuconostoc, PediococcusandStreptococcus, were screened for lipase production using an agar medium containing rhodamine b and three different lipid substrates, triolein (C18:1), tributyrin (C4:0), and butter oil. A total of 29 lipase-producing strains were identified. Assays using extracellular material (supernatant) and intracellular extracts (prepared by sonication) showed that lipases were produced as intracellular enzymes in the strains studied. Several different lipase assays were employed to measure lipase activities of lipases produced by selected lactic acid bacteria. The best lipase assay was the pH stat titrator, which gave quick, quantitative results of lipase activity toward a number of synthetic triacylglyceride substrates, as well as natural substrates, such as butter oil. Activities for cell free extracts ranged from <1.0–55 μmol free fatty acid released per minute per milligram of protein. However, lipase activities of extracts obtained from lactic acid bacteria were substantially lower than those reported for other micro-organisms, such asPseudomonasspp. andCandidaspp. Studies on the substrate specificity of selected lipases indicated the lipases were generally operating in a random fashion with regard to fatty acid type, although there was a slight preference for oleic acid.     

Effect of Soaking and Germination on Polyphenol Content and Polyphenol Oxidase Activity of Mung Bean (Phaseolus Aureus L.) Cultivars Differing in Seed Color

Five mung bean cultivars varying in seed coat color were analyzed for polyphenol content. The effect of soaking and germination on the polyphenol content and polyphenol oxidase activity was investigated. The level of total polyphenols was found to be in the range of 310–340 mg/100 g in whole seeds. Soaking reduced the total polyphenols, whereas germination for 48 h increased total polyphenol content by 41–76%. The hydrolysable tannins, condensed tannins, and hydrolysable tannins/condensed tannins index increased with an increase in period of germination. The total and percent condensed tannins content slightly decreased while hydrolysable tannins increased during germination. Maximum polyphenol oxidase activity of 102–108 units was observed in 24 h germinated seeds. There was no significant correlation found between the polyphenolic content and polyphenol oxidase activity in germinating mung bean seeds. These findings demonstrated that the mung beans are fair sources of polyphenols, thus having great potential as a source of natural antioxidants.     

不同处理对烟草种子萌发及过氧化氢酶活性的影响

以烤烟型品种NC89为材料 ,通过浸种处理研究了不同K+浓度、H+浓度、渗透势及H2 O2 等对烟草种子萌发过程中呼吸速率和过氧化氢酶活性的影响。 0 .0 1～ 0 .1mol/LKNO3处理对种子萌发过程中活力指数和过氧化氢酶活性有明显的促进作用 ;0 .0 0 1～ 0 .0 1mol/LHCl处理后其活力指数、第 4天的过氧化氢酶活性和呼吸速率都比对照高 ;2 0 0～ 30 0g/L的PEG - 6 0 0 0溶液浸种 2 4h ,对烟草种子活力的提高也有明显效果 ;0 .3%H2 O2 虽能提高烟草种子的呼吸速率 ,但其发芽势及活力指数均低于对照     

Rebuilding the lid region from conformational and dynamic features to engineering applications of lipase in foods: Current status and future prospects

The applications of lipases in esterification, amidation, and transesterification have broadened their potential in the production of fine compounds with high cumulative values. Mostly, the catalytic triad of lipases is covered by either one or two mobile peptides called the “lid” that control the substrate channel to the catalytic center. The lid holds unique conformational allostery via interfacial activation to regulate the dynamics and catalytic functions of lipases, thereby highlighting its importance in redesigning these enzymes for industrial applications. The structural characteristic of lipase, the dynamics of lids, and the roles of lid in lipase catalysis were summarized, providing opportunities for rebuilding lid region by biotechniques (e.g., metagenomic technology and protein engineering) and enzyme immobilization. The review focused on the advantages and disadvantages of strategies rebuilding the lid region. The main shortcomings of biotechnologies on lid rebuilding were discussed such as negative effects on lipase (e.g., a decrease of activity). Additionally, the main shortcomings (e.g., enzyme desorption at high temperatre) in immobilization on hydrophobic supports via interfacial action were presented. Solutions to the mentioned problems were proposed by combinations of computational design with biotechnologies, and improvements of lipase immobilization (e.g., immobilization protocols and support design). Finally, the review provides future perspectives about designing hyperfunctional lipases as biocatalysts in the food industry based on lid conformation and dynamics.     

金华火腿加工过程中内源脂肪酶活力变化特点研究

以浙江兰溪两头乌杂交猪后腿为原料,按传统工艺加工金华火腿。分别在原料、腌制结束、晒腿结束、成熟中期、成熟结束、后熟-1和后熟-2七个工艺点随机取5条腿的股二头肌为样品,分别测定中性脂肪酶、酸性脂肪酶的活力变化,以及测定pH5.8时脂肪酶综合活力的变化;同时,利用响应曲面法研究温度、盐含量、硝酸盐含量、亚硝酸盐含量对脂肪酶活力的影响,并利用所得回归方程预测金华火腿加工过程中脂肪酶的实际表现活力。结果表明,加工过程中,脂肪酶活力持续降低,在后熟-1工艺点,酸性脂肪酶和中性脂肪酶活力残留分别是8.16%和3.0%,至后熟-2已测不到酶活;温度、盐含量及其交互项是脂肪酶活力的显著影响因子(P<0.05),硝酸盐和亚硝酸盐含量对脂肪酶活力影响不显著(P>0.05)。加工过程中,预测的脂肪酶实际表现活力在成熟中期工艺点之前低于酸性脂肪酶及中性脂肪酶的潜在活力,之后则高于潜在活力,其变化规律与酸性和中性脂肪酶完全不同。     

萌发荞麦种子蛋白质组分含量变化的研究

研究了荞麦种子萌发后总蛋白质和各蛋白组分如清蛋白、球蛋白、醇溶蛋白和谷蛋白的含量变化，结果表明：本试验条件下，山西甜荞和四川苦荞萌发后总蛋白质含量呈逐渐下降趋势。山西甜荞经过72h的萌发，其蛋白质总量由最初的11．90％下降到5．44％，下降了6．5个百分点。四川苦荞由萌发初的6．53％下降到0．96％，下降了5．6个百分点。荞麦清蛋白和球蛋白在萌发后均呈现下降趋势，与总蛋白质含量变化相一致。谷蛋白在萌发后至36h内含量下降，之后又快速增加。四川苦荞醇溶蛋白含量在萌发后逐渐增加．而山西甜荞则有逐渐下降趋势。     

HORDEIN POLYPEPTIDE PATTERN IN RELATION TO MALTING QUALITY AND THE VARIETAL IDENTIFICATION OF MALTED BARLEY GRAIN

A procedure is described for the extraction of hordein fractions from single seeds of barley and determination of their polypeptide composition by SDS-PAGE. Varietal differences in the hordein polypeptide pattern occur, and on the basis of this character the 28 varieties which are most widely grown in the U.K. can be divided into 11 groups. Whereas several of these groups contain varieties with similar malting quality, other groups contain both good and poor quality varieties. Examination of pilot scale malts and germinating seeds showed little change in the hordein polypeptide pattern during malting or the early stages of germination. Thus the procedure is suitable for use in the identification of malted grain as well as dry seed.     

RELATIVE EFFICACY OF ESTER SYNTHESIS BY VARIOUS LIPASES IN MICROAQUEOUS MEDIA AND THE EFFECT OF WATER ON REACTION PROGRESS

Ten commercial sources of lipases were evaluated for comparative hydrolytic (in an aqueous emulsion) and ester synthesis (in microaqueous media) activities. There was little relationship between these activities for the lipases evaluated. An immobilized Rhizomucor miehei lipase had the greatest ester synthesis activity but had comparatively limited hydrolytic activity. For the five most effective ester synthesizing lipases, each had a characteristic optimum water content for maximum initial reaction rates. However, this optimum water content was greater than that associated with maximum reaction yield of ester formation, indicating the need for unique and differential moisture control during the progress of reaction to obtain maximum process efficiency.