葡萄糖浓度及补料方式对透明质酸发酵的影响

本研究以兽疫链球菌(Streptococcus zooepidemicus)为出发菌株,在10 L全自动发酵罐中进行透明质酸的发酵研究,考察葡萄糖浓度和补料方式对发酵结果的影响。结果显示,控制葡萄糖总浓度为80 g/L,采用初始葡萄糖浓度为40 g/L,一次性补加剩余40 g/L葡萄糖的方式时,菌体量和透明质酸的产量比分批培养时分别提高了13.5%和28.5%,乳酸的积累量降低7.89%,透明质酸的相对产率达到了10.02%,平均分子量达到了1.56×10~6u。因此,透明质酸的发酵生产可以采用补糖的方式提高生产强度和产品质量。     

透明质酸产生菌的复合诱变及摇瓶发酵条件的优化

采用紫外线、亚硝酸钠、亚硝基胍复合诱变的方法,得到遗传稳定性好、分子量高、透明质酸产量增幅3倍以上的突变株.在单因素试验的基础上,确定了影响兽疫链球菌透明质酸产量的关键因素为发酵时间、发酵温度和葡萄糖浓度.采用响应面法优化摇瓶发酵的条件,建立影响因子与其响应值之间的关系,结果表明:在摇瓶发酵温度32.47℃、发酵时间22.52h、葡萄糖浓度在65.46g/L条件下,透明质酸产量为0.562mg/mL.     

透明质酸发酵过程的动力学模型

构建透明质酸发酵动力学模型可反映发酵过程中菌体生长量、基质消耗量及透明质酸产量之间的变化规律。采用兽疫链球菌(Streptococcus zooepidemicus)进行摇瓶发酵,利用MATLAB软件对透明质酸含量、还原糖残量、菌体量的实验数据进行了非线性规划,建立了透明质酸生成动力学的模型。对拟合值与实验值进行比较,发现其吻合度较好,相对误差5%。本模型适用于培养基初糖质量浓度30 g/L的分批发酵,为透明质酸的产业化生产放大、发酵过程的工艺设计和管理控制提供科学的依据。     

透明质酸发酵过程的动力学模型

构建透明质酸发酵动力学模型可反映发酵过程中菌体生长量、基质消耗量及透明质酸产量之间的变化规律。采用兽疫链球菌（Streptococcus zooepidemicus）进行摇瓶发酵,利用MATLAB软件对透明质酸含量、还原糖残量、菌体量的实验数据进行了非线性规划,建立了透明质酸生成动力学的模型。对拟合值与实验值进行比较,发现其吻合度较好,相对误差＜5%。本模型适用于培养基初糖质量浓度＜30 g/L的分批发酵,为透明质酸的产业化生产放大、发酵过程的工艺设计和管理控制提供科学的依据。     

代谢工程改造谷氨酸棒杆菌合成透明质酸

透明质酸是一种被广泛应用于医药、化妆品和食品等领域的糖胺聚糖。透明质酸的主要工业生产菌株为兽疫链球菌,由于该细菌具有致病性,因此迫切需要构建安全的透明质酸生产菌株。通过在食品级表达宿主谷氨酸棒杆菌中异源表达透明质酸合酶基因(pmHasA),实现了透明质酸的合成,摇瓶中产量达到0.35 g/L。通过强化代谢途径中尿苷二磷酸-葡萄糖脱氢酶基因(ugdA2)和磷酸氨基转移酶基因(glmS)的表达以及敲除乳酸脱氢酶基因(ldh),透明质酸产量提高至0.81 g/L。在此基础上优化诱导条件,确定异丙基-β-D硫代半乳糖苷浓度为0.8 mmol/L,诱导剂添加时间为2 h时,摇瓶中透明质酸产量最高达到1 g/L。经过3 L发酵罐分批补料发酵,透明质酸产量达到4.8 g/L。该文通过调控谷氨酸棒杆菌代谢途径实现了透明质酸安全、高效的合成,为食品级透明质酸的生产奠定了基础。     

透明质酸补糖分批发酵工艺研究

采用马链球菌（Streptococcus equi）在7L自动发酵罐中进行分批补加葡萄糖发酵生产透明质酸（HA）。结果表明：采用葡萄糖初始浓度为35g／L,分批补加葡萄糖,使其浓度控制在20g／L-25g/L,通气量固定1．5L／min,通过调节搅拌转速（170r／min-300r/min）使发酵中后期溶氧控制在10％,可使HA的产量达到5．6g／L,平均分子量达到1．78×10^6u,较分批发酵时HA产量提高90％,分子量提高46％。     

培养条件对Streptococcus equisimilis合成透明质酸相对分子质量的影响

作者比较了不同培养条件对Streptococcus equisimilis合成透明质酸相对分子质量的影响。结果表明:高质量浓度葡萄糖有利于长链透明质酸的合成,当发酵体系葡萄糖初始质量浓度从20g/L上升至80g/L,相对分子质量从1.24×106增大到2.02×106,提高了62.9%。葡萄糖补料培养不利于高相对分子质量透明质酸的合成,利用葡萄糖间歇和连续补料培养的方式得到透明质酸相对分子质量分别为1.53×106和1.42×106,比分批培养下降了19.9%和25.7%。在33~39℃范围内,较低温度有利于高相对分子质量透明质酸的合成,在33℃培养条件下透明质酸相对分子质量最高可达2.54×106。发酵液p H显著影响透明质酸的相对分子质量,在p H8时,达到了最高的2.38×106。较高溶氧水平有利于高相对分子质量透明质酸的合成,在0~45%溶氧浓度范围内,相对分子质量随溶氧水平的增加从1.16×106提升至2.43×106,增长了109.4%。本研究结果为后续高相对分子质量透明质酸的生产提供有用的实验依据。     

透明质酸高产菌种选育及发酵条件优化

用NTG和LiCl复合诱变,筛选不产溶血素和透明质酸降解酶的突变菌株,对发酵条件进行优化,在最佳发酵条件下,透明质酸的产量达到5.68g/L,分子量达到1.06×106Da。     

链球菌分批发酵生产透明质酸及其动力学研究进展

透明质酸(HA)是一种具有特殊生理功能的高分子糖,在医药和化妆品工业中有着广泛的应用.本文综述了近年来透明质酸发酵研究的一些进展,并介绍了分批发酵中不同初糖浓度,pH,搅拌转速对菌体生长和产物形成过程的影响及透明质酸发酵动力学模型.     

透明质酸产生菌发酵条件优化

通过对于透明质酸产生菌发酵培养基,利用Placken-Burman设计及响应面试验分析了摇瓶培养基成分,确定了最适合的摇瓶发酵培养基.通过小型发酵罐的研究确定了透明质酸的发酵工艺.实验结果表明,利用响应面实验优化的培养基组分简单.透明质酸的产量达到5.23 g/L,分子量为2.0×106u.     

乳酸乳球菌L9产类细菌素lactococcin GJ-9发酵条件的研究

对产类细菌素乳酸乳球菌L9的发酵条件进行了研究。结果表明 :产类细菌素最适培养基为MRS,培养基的最适初始pH值为 6 5 ;产类细菌素最适温度为 32℃ ;0 2 %Tween 80最适类细菌素的产生。并通过正交试验确定L9产类细菌素的最佳培养基为 :大豆蛋白胨 1 %、酵母膏1 5%、葡萄糖 1 2 5 %、K2 HPO40 2 %、NaAc 0 5 %、MgSO4·7H2 O 0 0 58%、柠檬酸三铵 0 2 %、MnSO4·4H2 O 0 0 0 5 %、Tween 80 0 2 % ;初始 pH6 0。经过优化 ,发酵液效价提高了 61 0 7%。     

利用Crypthecodinium cohnii高密度发酵生产DHA的流加策略研究

利用流加策略实现了隐甲藻(Crypthecodinium cohnii)生产DHA的高密度发酵。根据隐甲藻间歇式发酵的特性,探讨最佳补料时间及流加液中最佳碳氮比,结果表明,在葡萄糖浓度降至4g/L左右时流加碳氮比为30∶1的营养液对隐甲藻的生长和脂肪酸积累最有利。根据以上结果,初始葡萄糖浓度25g/L,采用5d连续发酵多次流加策略,细胞干重达6.37%,DHA产量为4.08g/L。     

植物乳杆菌最适生长底物解析及高密度培养工艺

为提高植物乳杆菌的增殖浓度,分别测定菌株在添加不同氮源、不同缓冲盐、不同浓度的MnSO₄和不同促生长物质时菌株的生长浓度。结果表明,酵母类氮源是植物乳杆菌的最适氮源,缓冲盐在恒pH培养时对菌株生长无促进作用,锰浓度与最高活菌数呈正相关,在以酵母浸粉为氮源时植物乳杆菌培养不需要添加其他生长因子。进一步优化菌株的最适pH值和碳氮比,基于可耐受渗透压,优化恒pH培养和恒pH自动反馈补料培养基和培养工艺,得到各菌株的最适培养策略。3株菌的最适氮源添加量为40～45 g/L,MnSO₄的最适添加量为0. 25 g/L,最适碳氮比为对数生长期生长速率被抑制时的碳氮消耗比。恒pH 5. 5自动反馈补料培养植物乳杆菌X1,活菌数达到4. 1×10¹⁰CFU/mL;恒pH 5. 5分批培养植物乳杆菌N8,活菌数达到2. 9×10¹⁰CFU/m L;恒pH 6. 0分批培养植物乳杆菌N9,活菌数达到6. 2×10¹⁰CFU/mL。该研究结果的应用将显著提高植物乳杆菌的工业化生产效率。     

Lactobacillus delbrueckii营养条件的研究

研究了L delbrueckiiYJS 2 1的营养要求 ,结果表明 ,L delbrueckiiYJS 2 1缺乏合成L 谷氨酸、L 天冬氨酸、L 色氨酸、L 异亮氨酸的能力 ;生物素、对氨基苯甲酸、硫胺素对L delbrueckiiYJS 2 1生长及产酸有明显的促进作用。同时利用正交设计优化得到了最佳生长因子 :L 谷氨酸 30mg/L、L 天冬氨酸 8mg/L、L 色氨酸 1 2mg/L、L 异亮氨酸 6mg/L、生物素 180 μg/L、对氨基苯甲酸 4mg/L、硫胺素 2 0mg/L。在最适发酵条件下 ,乳酸产量、对糖转化率、乳酸生产率分别为 14 0 3g/L、93 5 %、1 95 g/ (L·h)。     

糖质原料直接发酵生产L-苹果酸的工艺条件

以黄曲霉HA5 80 0为出发菌株 ,研究探讨了不同碳源、氮源、无机盐类以及温度等因素对糖质原料直接发酵生产L 苹果酸的影响 ,产L 苹果酸突变株黄曲霉HA5 80 0适合于多种原料的L 苹果酸发酵 ,如液化淀粉、脱脂玉米粉、葡萄糖、淀粉水解糖等 ;氮源以玉米浆与硫酸铵配合使用为最佳 ;实验中确定了较优培养基组成和发酵工艺条件 ,适宜的发酵温度为 34～ 36℃ ;向培养基中添加CaCO3 是L 苹果酸有效积累的必要条件 ,初糖控制在 10 0～ 12 0 g/L时 ,适宜的CaCO3 用量为70～ 80 g/L ,L 苹果酸产率达 80～ 90g/L。     

High butanol production by Clostridium saccharoperbutylacetonicum N1-4 in fed-batch culture with pH-Stat continuous butyric acid and glucose feeding method

A pH-stat fed-batch culture by feeding butyric acid and glucose has been studied in an acetone-butanol-ethanol (ABE) fermentation using Clostridium saccharoperbutylacetonicum N1-4. The specific butanol production rate increased from 0.10 g-butanol/g-cells/h with no feeding of butyric acid to 0.42 g-butanol/g-cells/h with 5.0 g/l butyric acid. The pH value in broth decreases with butyric acid production during acidogenesis, and then butyric acid reutilization and butanol production result in a pH increase during solventogensis. The pH-stat fed-batch culture was performed to maintain a constant pH and butyric acid concentration in the culture broth, but feeding only butyric acid could not support butyric acid utilization and butanol production. Subsequently, when a mixture of butyric acid and glucose was fed, butyric acid was utilized and butanol was produced. To investigate the effect of the feeding ratio of butyric acid to glucose (B/G ratio), several B/G ratio solutions were fed. The maximum butanol production was 16 g/l and the residual glucose concentration in broth was very low at a B/G ratio of 1.4. Moreover, yields of butanol in relation to cell mass and glucose utilization were 54% and 72% higher in pH-stat fed-batch culture with butyric acid than that of conventional batch culture, respectively.     

Kinetics analysis of growth and lactic acid production in pH-controlled batch cultures of Lactobacillus casei KH-1 using yeast extract/corn steep liquor/glucose medium

This study was performed to determine the optimal conditions of yeast extract, corn steep liquor and glucose concentration for the growth and lactic acid production of Lactobacillus casei KH-1 and to assess the effect of these conditions using a response surface methodology. A Box-Behnken design was used as an experimental design for the allocation of treatment combination as 17 pH-controlled batch cultures. The growth and product parameters were estimated by Gombertz, Leudeking and Piret models from experimental data, and analyzed statistically with response surfaces. The effects of yeast extract, corn steep liquor and glucose were significant for the maximum specific growth rate, mu(max) and the maximum biomass concentration, X(ma). The interaction of corn steep liquor and glucose indicated that the positive or negative effect of glucose on mu(max) in corn steep liquor below or above 2.1% could be explained by the glucose-dependent availability of a nutrient on mu(max) Although the experiment was achieved in pH-controlled batch culture for L. casei KH-1, the growth- and non-growth-associated production rate parameters, a and b, were significant in the response surface model. The growth and lactic acid production of L. casei KH-1 were strongly affected by glucose and the importance of the media composition was demonstrated. The estimated optimal conditions of the growth and lactic acid production of L. casei KH-1 were 1.276% and 0.697% for yeast extract, 3.505% and 1.708% for corn steep liquor, and 2.390% and 2.215% for glucose, respectively.     

Effect of the cultivation mode on red pigments production from Monascus ruber

In submerged cultures performed in chemically defined fermentation medium containing glucose and glutamate, the growth and production of water‐soluble red pigments and citrinin by the filamentous fungus Monascus ruber were studied under various carbon/nitrogen (C/N) ratios. The specific production of the red pigments was optimal at a glucose/glutamate ratio of about 10 and then steadily decreased at higher C/N ratio. In contrast, the production of the mycotoxin increased with increased C/N with an optimum in the range of 30–45. In a fed‐batch mode, it was also found that the production of pigments was not favoured in fed‐batch mode by feeding the medium with glucose while keeping the C/N ratio lower than 10. This low production likely resulted from concurrent high accumulation of L‐malic acid that was reported to inhibit this production. In contrast, this mode of cultivation was rather favourable for the production of the mycotoxin.     

Fed‐batch fermentation with glucose syrup as an adjunct for high‐ethanol beer brewing

To produce a beer with a high ethanol content, preliminary research on fed‐batch fermentation profiles with glucose syrup as an adjunct during the primary fermentation period was conducted. The ethanol concentration of the beer was elevated by feeding a glucose syrup into the fermentors at a later stage of primary fermentation. Fermentation trials were carried out using a typical lager strain, SC‐9, with a pitching rate at 7.0 × 10⁶ cells/mL. An all‐malt wort (12.5°P) was employed and the primary fermentation temperature was 14 °C. Glucose syrup was supplemented when the concentration of residual reducing sugars was decreased to ~10 g/L. Results showed that the supplemented glucose was consumed rapidly and that the ethanol concentration in the final beer was raised to 67.9 g/L. Additional growth of yeast was observed after feeding accompanied by a low yield of ethanol (~0.46 g/g). Formation of diacetyl was enhanced by yeast growth and two additional peaks were obtained after feeding. The peak value of the diacetyl concentration was 1.90 mg/L. The fed‐batch fermentation resulted in a beer with an overproduction of higher alcohols and esters, indicating that brewing under these experimental conditions led to an unbalanced flavour profile. Results of optimization demonstrated that the optimal conditions were found to be 15°P for initial wort extract, 10 °C for fermentation temperature and 20 × 10⁶ cells/mL for yeast pitching rate, leading to total higher alcohols of 173.8 mg/L, total esters of 22.8 mg/L and an acetaldehyde concentration of 40.5 mg/L. A 12 day maturation and fermentation temperature of 8 °C was needed to reduce the acetaldehyde to 14.3 mg/L. Copyright © 2014 The Institute of Brewing & Distilling     

Enhanced 2,3-butanediol production by addition of acetic acid in Paenibacillus polymyxa

By the addition of 150 mM acetate into a batch culture at an initial pH of 6.8, the production of 2,3-butanediol (BDL) by Paenibacillus polymyxa reached 248 mM, yielding 0.87 mol.mol(-1) glucose, where the ratio of acetate consumed to glucose consumed (A/C ratio) was calculated as 0.35 mol acetate mol(-1) glucose. Therefore, a fed-batch culture was carried out by feeding glucose and acetate at a ratio of 0.35 mol acetate mol(-1) glucose. In the fed-batch culture performed at pH 6.8, BDL production reached 637 mM, yielding 0.81 mol.mol(-1) glucose, although the A/C ratio was only 0.18 mol acetate mol(-1) glucose. By decreasing pH to 6.3 in the fed-batch culture, BDL production reached 566 mM, yielding 0.88 mol.mol(-1) glucose and the A/C ratio was 0.32 mol acetate mol(-1) glucose. The optical purity of BDL, which was expressed as enantiomeric excess, was retained at more than 98% of the (R, R)-stereoisomer at the end of culture, which was comparable to that without acetate addition.