Isolation and characterization of a hexokinase mutant of Schwanniomyces castellii: Consequences on cell production in continuous culture

A mutant of Schwanniomyces castellii with reduced glucose phosphorylation and with practically no phosphorylation of fructose was investigated. Carbon catabolite represion of α-glucosidase and amylases was reduced. Repression of β-galactosidase was normal. We have compared in continuous culture this mutant strain with wild type and another previously described mutant. The relationship between the specific rate of glucose consumption (Qs) and residual glucose concentration (s) in an inverse mode, suggests that there may be two types of transport of glucose. Mutation at the phosphorylation level causes apparent modification of the kinetic parameters of glucose uptake rate. The consequence of mutation at the phosphorylation level on biomass production was discussed.     

Effect of adsorbent particle size and temperature on water-ethanol separation by starchy and cellulosic substrates

Inverse gas chromatography was used to study the adsorption of water and ethanol on two starchy (cornmeal and wheatflour) and one cellulosic (wheat straw) substrate, in the temperature range 50–90??°C. Three particle size fractions of each substrate were investigated – 180–250?μm, 160–180?μm and 125–160?μm, denoted, respectively, by: 60–80 mesh, 80–100 mesh and 100-120 mesh. Values for the separation factor and for thermodynamic parameters, such as Gibbs free energy and enthalpy of adsorption, were calculated from the chromatographic retention data. The results showed that water was adsorbed more strongly than ethanol on all substrates, at all temperatures. In addition, it was found that lower temperatures were more favourable for the adsorption of both solutes. There was no significant difference between values of separation capacity of the three fractions of wheat straw. In contrast, the separation capacities of starchy materials with smaller particle sizes, i.e. 80–100 mesh and 100–120 mesh, were greater. The 100–120 mesh wheatflour fraction exhibited the highest separation at all temperatures.     

Water and ethanol adsorption on starchy and cellulosic substrates as biomass separation systems

Adsorption of water and ethanol on to one cellulosic and five starchy materials of constant particle size has been studied in the temperature range of 50?–?90°C using inverse gas chromatography (IGC). The results showed that all substrates adsorbed water to a greater extent than ethanol, at all temperatures. On the other hand, the type of adsorber affected the adsorption of water more significantly than that of ethanol. Starchy materials showed a greater separation capacity compared to the cellulosic material. From the chromatographic retention data it was possible to calculate the separation factors for the two solutes and to obtain values for thermodynamic parameters such as Gibb’s free energy (ΔGs) and the enthalpy (ΔHs) of adsorption of water and ethanol on to the substrates. Calculated ΔGs values revealed that the adsorption of both solutes was more spontaneous at lower temperatures, as expected. The ΔHs values obtained for water were significantly higher than those for ethanol, indicating stronger water/substrate interactions. Wheatflour of 70% rate extraction proved to be the substrate with the highest separation factor at all temperatures.     

高效液相色谱法同时检测淀粉类食品中添加的姜黄色素与类胡萝卜素化合物

建立了淀粉类食品中姜黄色素与类胡萝卜素化合物的高效液相色谱分析方法。方法 采用环已烷-乙酸乙酯二元体系提取试样中姜黄素、去甲氧基姜黄素、双去甲氧基姜黄素、叶黄素和β-胡萝卜素,硅胶SPE柱净化,YMCTM Carotenoid 色谱柱(250 mm×4.6 mm,5 μm)分离,甲基叔丁基醚和甲醇-水梯度洗脱。对所分析化合物的稳定性、前处理条件及色谱条件进行了探讨与优化。结果 5种分析物在0.5～100 μg/ml范围内线性关系良好,相关系数为0.998 4～0.999 8。在1～100 mg/kg浓度范围内,平均加标回收率为68.5%～101.2%,相对标准偏差为3.4%～10.4%。定量限为1 mg/kg。结论 本方法稳定、可靠,可应用于实际样品的检测。     

高效液相色谱法检测淀粉及含淀粉食品中6种有机酸

研究了应用高效液相色谱法检测淀粉及淀粉类食品中顺丁烯二酸、反丁烯二酸、苹果酸、琥珀酸、酒石酸、乙酸等6种有机酸的测定方法。利用SAX色谱柱连接C18预柱的方法,实现了对上述有机酸的完全分离。研究了分析方法的线性、灵敏度和精密度,结果在所确定的实验条件下,6个有机酸的线性系数大于0.999,在淀粉及淀粉类食品中的加标回收率处于75%⁹5%之间,变异系数均小于5.0%。     

液体发酵时间对2种虫草固体栽培的影响

探索蛹虫草和高雄山虫草固体培养时种子液的最佳接种时间,以期为其的工业化生产提供科学依据.采用常规方法接种和计数,以液体发酵的菌丝干重、菌丝段和固体培养基上的菌丝覆盖率为指标,结果表明,2种虫草在液体发酵条件下,第3d～6d为菌株快速生长期,活力旺盛,适合转接,尤其是发酵4d的种子液接种到固体培养基上其生长速度最快,生长状况最好,长满固体培养基的时间最短.     

香菇产抑菌活性物质液态发酵条件优化

以抑菌活性为评价指标,以接种量、初始pH值、摇床转速、发酵时间、发酵温度为考察因素,采用单因素及正交试验优选液态发酵条件.结果表明,产抑菌活性物质的最佳发酵条件是接种量7％,发酵液初始pH值为5,培养时间8d、培养温度为28℃.在此条件下,发酵液对黄曲霉的抑菌圈直径为8.9 cm.发酵液初始pH值和发酵时间对试验结果的影响显著.     

Simultaneous production of natural statins and coenzyme Q10 by Monascus pilosus fermentation using different solid substrates

Simultaneous production of mevinolins (natural statins) and ubiquinones (coenzyme Qs; CoQ₉ and CoQ₁₀) were identified and determined in solid substrates fermented (SSF) with Monascus pilosus K-1140. The highest co-production of mevinolins (2.31±0.11 mg/g) and ubiquinones (0.24±0.02 mg/g) was obtained in a mixed grains substrate (rice:sorghum:barley:buckwheat:soybean; 1:1:1:1:1; w/w/w/w/w). The optimal conditions for mixed grains in the SSF were initial moisture content of 50% and initial substrate pH of 6. The total production of CoQs was increased by 32% with the addition of red paprika. Mevinolinic acid (hypocholesterolemic agent) was the main component contributing 81.3 to 91.5% of total mevinolins in the fermented substrates. The results indicate that mixed grain fermented with M. pilosus may be used as a new nutraceuticals with anti-atherosclerotic function without statin-induced CoQ₁₀ deficiency.     

固相萃取-高效液相色谱法测定食品基质中5种不同合成红色着色剂

目的建立一种固相萃取-高效液相色谱法(solidphaseextraction-highperformanceliquid chromatography,SPE-HPLC)测定食品中5种人工合成红色着色剂(新红、苋菜红、胭脂红、诱惑红、赤藓红)的方法。方法比较ProElut PWA-2, Cleanert PWAX和Sep-Pak Plus QMA 3种不同SPE小柱的净化效果,比较Eclipse XDB C_(18)、Venusil XBP C_(18)及Agilent TC-C_(18) 3种色谱柱对5种着色剂的分离情况,按照GB 5009.35-2016《食品中合成着色剂的测定》对食品中5种着色剂进行测定。结果 Pro Elut PWA-2 SPE固相萃取小柱进行样品净化效果最优, Agilent TC-C_(18)色谱柱在10 min内有较好的分离度。加标浓度为0.5～50 mg/kg时,该方法回收率为90.3%～103.9%,相对标准偏差(relative standard deviation, RSD)值为1.18%～7.11%。结论该方法快速、准确,适合用于不同食品基质中5种合成着色剂定性、定量测定。     

Characteristics of alpha-glucosidase production from recombinant Aspergillus oryzae by membrane-surface liquid culture in comparison with various cultivation methods

alpha-Glucosidase was produced using recombinant Aspergillus oryzae by membrane-surface liquid culture (MSLC), a method previously developed by the authors and the results compared with other methods, including shaking flask culture (SFC), agar-plate culture (APC), culture on urethane sponge supports (USC), and liquid surface culture (LSC) to determine possible reasons for the advantageous features of MSLC. When yeast extract was used as a nitrogen source, the amount of enzyme produced by MSLC was 5 or more times higher than those for SFC and LSC, but similar to that using APC. Enzyme production in USC was slightly lower than in MSLC and APC. Cell growth was similar irrespective of the cultivation method used. When NaNO3, a typical inorganic nitrogen source was used, enzyme production in all the cultures was lower than that using yeast extract. However, even using NaNO3, the amount of the enzyme produced by MSLC was 8 to 20 times higher than those by SFC, APC, USC, and LSC. Although cell growth using NaNO3 was similar to that for yeast extract in MSLC, it was markedly decreased in SFC, APC, and LSC. The reason for the difference in enzyme productivity for various cultivation methods using yeast extract and NaNO3 as a nitrogen source is discussed, on the basis of the experimental findings. The role of the oxygen transfer effect and gene expression levels in enzyme production were also examined.     

固态发酵白酒生产工艺过程分析

介绍了固态发酵白酒较液态发酵白酒的优点,并指出我国固态发酵白酒生产工艺的现状及存在问题,最后对固态发酵白酒的生产工艺流程进行分析。     

高效液相色谱-二极管阵列法检测复杂食品基质中爱德万甜含量

目的优化流动相配比、柱温、检测波长等条件,建立高效液相色谱-二极管阵列法检测复杂食品基质中爱德万甜含量的分析方法。方法样品经前处理后,在磷酸缓冲液和乙腈洗脱下,经C18硅胶柱分离,于210 nm波长处进行定量检测,并根据280 nm处特征吸收进行定性检测。结果在0.2～100μg/mL范围内,出峰面积与质量浓度呈良好的线性相关(r~2=0.99998)。在果蔬汁、饼干、饮料、酱腌菜等食品中,爱德万甜的检出限为0.02μg/mL、定量限为0.08μg/mL,且该方法对不同样品基质中的加标回收率为89.6%～106.2%。结论该方法操作简便、灵敏度高,适用于果蔬汁、饼干、饮料、酱腌菜中爱德万甜的检测。     

酯化红曲霉菌液态培养条件研究

以红曲霉为原始菌株,经分离筛选获得1株产酯能力较高的红曲霉菌,并对其培养基配方和培养条件进行了研究。试验结果表明,液态发酵培养红曲霉的最佳培养基组成为可溶性淀粉70g/L,黄豆饼粉10g/L,酵母浸膏10g/L,MgSO41g/L,NaNO32 g/L,NaH2PO4 1 g/L;最佳发酵条件为培养基初始pH值为4.5,接种量16%,装液量100mL/300mL,发酵时间为6d,红曲霉的酯化力达0.4678g/100mL。     

Plackett-Burman设计法筛选影响茎点菌属在液体培养中生产松脂醇二葡萄糖苷的主要影响因子

在单因素试验的基础上,选定合适的因素水平,通过Plackett-Burman设计从5个因素中筛选出培养基初始pH、摇床转速、装液量是影响茎点菌属菌SP-16F生产松脂醇二葡萄糖苷(PDG)的主要因素,其较优水平为初始pH8、转速180 r/min、装液量100 mL/250 mL.在试验条件下,PDG的最高产量可达29 mg/L.     

固相萃取-高效液相色谱法测定蔬菜中三唑酮、 百菌清和乙烯菌核利残留量

目的建立固相萃取-高效液相色谱-二极管阵列检测法测定蔬菜中三唑酮、百菌清和乙烯菌核利残留量的方法。方法蔬菜样品用乙腈超声提取,加入氯化钠进行盐析脱水,提取液过中性氧化铝柱净化,用正己烷/丙酮(90:10,V:V)淋洗液洗脱,洗脱液水浴氮吹近干,流动相定容后采用高效液相色谱法进行测定,外标法定量。结果三唑酮、百菌清和乙烯菌核利质量浓度在0.02~5.0 mg/L范围内与其峰面积呈良好的线性关系,方法检出限为0.02 mg/kg,加标回收率为89.5%~105.1%,精密度(relative standard deviation,RSD)为0.85%~4.25%。结论该方法操作简单、准确,可应用于蔬菜中三唑酮、百菌清和乙烯菌核利的检测。     

固态发酵生产活性干酵母的研究

以酿酒活性干酵母为对象,以麸皮、玉米粉、米糠为基本原料,经固态培养基选择优化,酵母细胞数高于4.47×109 CFU/g.在此基础上加入一定量糖化酶、酸性蛋白酶,并对培养基进行优化,酵母细胞数高达6.0×109 CFU/g.另外,在载体培养初步研究中,把玉米水解液加到多孔性材料中进行酵母培养,酵母细胞数高于5.0×108 CFU/mL.     

高效液相色谱法测定固体饲料中的二氢吡啶

目的建立一种高效液相色谱测定固体饲料中二氢吡啶含量的分析方法。方法样品经乙腈超声提取、高速离心后旋蒸浓缩,以乙腈和超纯水为流动相,采用高效液相色谱-二极管阵列检测器对固体饲料中二氢吡啶进行检测。结果二氢吡啶在0.26~140μg/m L浓度范围内线性关系良好(r~20.999),回收率在81.6%~94.6%之间,相对标准偏差为0.3%~4.0%,方法检出限为0.04 mg/kg。结论本方法具有前处理简便、准确度高、精密度高和可靠性好等优点,可适用于畜禽饲料、水产饲料等常温下为固态的饲料基质中二氢吡啶的检测。     

Overview on mitigation of acrylamide in starchy fried and baked foods

Acrylamide in fried and baked foods has the potential to cause toxic effects in animals and humans. A major challenge lies in developing an effective strategy for acrylamide mitigation in foods without altering its basic properties. Food scientists around the world have developed various methods to mitigate the presence of acrylamide in fried food products. Mitigation techniques using additives such as salts, amino acids, cations and organic acids along with blanching of foods have reduced the concentration of acrylamide. The use of secondary metabolites such as polyphenols also reduces acrylamide concentration in fried food products. Other mitigation techniques such as asparaginase pre‐treatment and low‐temperature air frying with chitosan have been effective in mitigating the concentration of acrylamide. The combined pre‐treatment process along with the use of additives is the latest trend in acrylamide mitigation. © 2018 Society of Chemical Industry     

米曲霉固态发酵产酶条件及酶活力研究

以酱油生产用米曲霉沪酿3.042进行固态发酵,考查了影响米曲霉蛋白酶、木聚糖酶、纤维素酶生产的固态发酵条件,包括碳源、氮源、初始pH值及温度等因素.实验表明,此菌株产酶的最佳碳、氨源分别为麸皮及蛋白胨,最适合产酶的初始pH值为6.0～8.0,温度为30℃.实验并对菌株所产的蛋白酶、纤维素酶、木聚糖酶进行了活力分析,为深入研究及应用米曲霉酶系提供理论依据.