通气量和菊粉浓度对克鲁维酵母乙醇发酵的影响

马克斯克鲁维酵母能够利用集成生物加工技术发酵菊芋生产乙醇,具有非粮燃料乙醇生产潜力.文中研究了该技术中的两个关键因素(通气量和底物浓度)对于K.marxinaus YX01乙醇发酵过程和菊粉酶活性的影响.研究结果表明,底物浓度对乙醇得率影响不大,底物浓度为250 g/L时,发酵终点乙醇浓度为84.74 g/L,但乙醇得率由低浓度50 g/L的86.4％(理论值),降为84.7％.通气能够加速K.marxinaus YX01的乙醇发酵过程,但降低了乙醇得率,当底物浓度为250 g/L时,乙醇得率由不通气的84.7％降为1.0 vvm时的73.3％.随底物浓度的升高及通气量的降低,K.marxinaus YX01分泌的菊粉酶活力表现出降低的趋势.在不通气及底物浓度为250 g/L时,菊粉酶的活性为6.59 U/mL,而底物浓度50 g/L,通气量1.0 vvm时的酶活力为21.54 U/mL.乙醇发酵过程中的副产物甘油随通气量的降低及底物浓度的升高而增大,而乙酸的浓度随通气量的增大及底物浓度的升高而升高.     

溶氧对Blakeslea trispora分批发酵生产β-胡萝卜素的影响

在摇瓶和5 L发酵罐中研究了溶氧 (DO) 对Blakeslea trispora分批发酵生产β-胡萝卜素的影响,总结了5 L发酵罐中β-胡萝卜素发酵过程中溶氧的变化规律.结果表明,当500 mL摇瓶装液量为50 mL,转速为240 r/min条件下发酵生产β-胡萝卜素产量最大,达到3.416 g/L; 5 L发酵罐中,在搅拌转速为1 000 r/min,通气量为1.5 vvm的条件下,β-胡萝卜素的产量可达到3.712 g/L,略高于摇瓶,这可能是由于5 L发酵罐中的气液传递和混合状况好于摇瓶,促进了产物的合成.     

搅拌和通气对裂殖壶菌LX0809产DHA的影响

利用一株生产DHA专利菌株裂殖壶菌LX0809,在10 L全自动发酵罐中考察了16个搅拌转速和通气量组合对裂殖壶菌LX0809发酵产DHA的影响。生物量和总油脂的产量随搅拌转速和通风量的增加而增加,DHA占总油脂比例随搅拌转速和通风量的增加而降低,最终确定通气量为全程0.3 m3/h(通气比0.83),搅拌转速为前40 h 400 r/min,后56 h 300 r/min。发酵96 h放罐,细胞生物量92 g/L,油脂质量浓度52.3 g/L,DHA占总油脂含量为40.2%,DHA发酵产量高达21 g/L。     

通气量对气升式反应器培养高山被孢霉生产花生四烯酸的影响

高山被孢霉具有很强的积累花生四烯酸(ARA)的能力,通过对30 L气升式反应器发酵过程的通气量进行调控,结果发现:通气量对高山被孢霉菌体生长、形态及ARA合成具有显著影响。中等大小的球形菌丝形态有利于菌体持续生长和油脂积累,ARA占总油脂的含量最高,而羽状菌丝形态菌体中总油脂含量和ARA含量均小于球形菌丝形态菌体中的含量。通气量为1.0 vvm(1 vvm为每分钟通气量与罐体实际料液体积之比)时有利于菌体保持良好形态和生长,通气量为1.4 vvm有利于发酵对数期后(72~168 h)ARA的积累。提出一种两阶段通气量控制策略,在气升式发酵罐中高山被孢霉的菌丝形态得到显著改善,ARA产量达到4.72 g/L,比对照提高了40.1%。     

摇床转速对淡紫拟青霉菌生长的影响

设置不同摇床转速来调节通气量,以淡紫拟青霉菌株NHPL03培养过程的OD值、pH值、菌丝重量、孢子量、毒力为指标,研究通气量对淡紫拟青霉菌NHPL03生长的影响。结果表明:淡紫拟青霉菌可在多种摇床转速(通气量)条件下生长。通气量不仅影响菌丝生长与孢子生成而且影响毒力产物分泌,菌丝生长与孢子生成的最佳摇床转速为100r/min,培养8d菌丝干重达到最高值1.10g/50mL,产孢量达28.5×106个/mL。从毒力强度看,低转速条件60r/min总体毒力水平最高,培养8d菌液对茎线虫校正致死率达到47.1%。     

提高蛋白激发子产量的培养基及发酵条件的优化

为了进一步提高极细链格孢菌产蛋白激发子的产量,通过单因子和多因子试验与分析,筛选优化了适于极细链格孢菌产生蛋白激发子的培养基和培养条件,并检测了发酵过程中pH、还原糖、氨基氮和菌丝量变化以及与蛋白激发子产量的关系。结果表明,土豆淀粉和黄豆粉对蛋白激发子产量影响最大,其次是蛋白胨和无机盐。优化的发酵培养基主要成分（g／L）：碳源I 15、葡萄糖5、玉米淀粉5、土豆淀粉20、谷氨酸10、氮源I5、黄豆粉10、硫酸铵5。确定了优化的培养条件,调整培养基起始pH为7．0～7．5,将18h菌龄的种子培养液按10％接种量接种到装液量为75mL的500mL摇瓶中,在温度（28±1）℃、摇床转速180r／min下培养可获得理想的蛋白产量。在优化的培养基和培养条件下,发酵12～48h该菌进入对数生长期,48h进入稳定生长期,60h菌丝扣蛋白激发子产量达最高。蛋白产量与菌体生物量呈正相关,当还原糖、总糖量消耗到最低水平时,菌丝产量和蛋白激发子产量达最高。优化的培养基菌丝干重收率迭3．9g／100mL,蛋白激发子产量达到5．17g／L,比普通的土豆液体培养基提高近4倍。     

药用蕈菌紫芝液体培养的生长特征分析

使用专门设计的ALR ff蕈菌液体培养反应器 ,研究了有关紫芝液体培养过程中菌丝生长的特征。结果表明 ,液体培养时紫芝菌丝生长对温度有较宽的适应范围 2 5℃～ 3 5℃ ,但生长比速率相差很大。通气量由 0 93vvm提高到 1 6 4vvm时 ,菌丝生长比速率明显地增加 ,最大值为 0 0 4 4 4 (h- 1) ;当通气量进一步提高到 2 5 0vvm时 ,生长比速率反而下降。与低糖浓度比较 ,较高糖浓度 (2 80g 1 0 0mL)可以使生长迟滞期缩短 ;培养后期菌丝缠绕成浓密颗粒 ,较高糖浓度可以促进生长。在整个培养过程中 ,糖浓度较低时葡萄糖转化成菌体的生长效率明显高于较高葡萄糖浓度的效率。碳源限制生长的连续培养研究结果 ,进一步反映了菌丝不同生长活性使菌丝物具有不同形态结构。菌体量、限制生长底物、菌体生成率的三者关系与细菌有明显的差异。并且 ,在 0 0 1 0～ 0 2 2 0 (h- 1)稀释率范围内菌丝生长符合Contois方程     

L-精氨酸高产菌红曲霉的筛选及发酵初步研究

对不同样品中的真菌进行了L-精氨酸高产菌株的筛选,从红曲米中分离出1株高产L-精氨酸菌株红曲霉H13,其初始发酵液中L-精氨酸产量为1.67 g/L.通过单因素实验对其液体发酵进行研究.结果表明,最佳碳源是可溶性淀粉,最佳浓度为10％,最佳氮源是蛋白胨,最佳浓度为3％,最佳pH值4.5,温度30℃,种子培养时间为18 h,摇瓶装液量50 mL/250 mL.转速为120 r/min,发酵时间7d.在此条件下进行发酵培养,所得发酵液产L-精氨酸4.08 g/L,菌丝体干重为10.32 g/L,菌丝体中L-精氨酸含量为24.17 mg/g.     

真姬菇液体发酵培养基筛选及硒富集条件优化

以真姬菇菌种为材料,采用液体摇瓶培养进行最适发酵培养基的优化,并探讨不同浓度亚硒酸钠和甘油的富硒效果。结果表明:真姬菇菌种最优液体发酵培养基为:马铃薯20%,麦麸滤液3%,可溶性淀粉3%,酵母粉0.15%,硫酸镁0.1%,磷酸二氢钾0.2%,最大生物量可达13.2 g/L;亚硒酸钠对菌丝生长有抑制作用,但可促进菌丝富硒,当其浓度为40μg/mL时,菌丝体的硒含量最大,达1.75μg/g,总体硒富集含量可达5.8μg/L发酵液;甘油对亚硒酸钠的总富硒含量有促进作用,当甘油浓度为50μg/mL时,菌丝总体硒富集含量最大,可达26.7μg/L发酵液。     

珍稀药用真菌——樟芝深层发酵培养条件的优化

对樟芝深层发酵培养基进行了筛选,并在此基础上对发酵条件进行了优化。以樟芝深层发酵菌丝体三萜产量为主要目标产物,确定发酵培养条件为:40g/L葡萄糖,6g/L豆饼粉,1g/L K_2HPO_4,0．5g/L MgSO4,VB_1 100mg/L,自然pH,接种量为20%,装液量为100mL/250mL三角瓶,转速100r/min,26℃恒温培养6d,胞内三萜产量达15．25mg/100mL发酵液。     

Effect of agitation and aeration on the citric acid production by Yarrowia lipolytica grown on glycerol

The effects of agitation rates from 400 to 900 rpm and aeration rates ranging from 0.18 to 0.6 vvm on biomass and citric acid production on glycerol media by acetate-negative mutants of Yarrowia lipolytica, Wratislavia 1.31 and Wratislavia AWG7, in batch culture were studied. The agitation rates of 800 and 900 rpm (at a constant aeration rate of 0.36 vvm) and aeration rates within the range of 0.24-0.48 vvm (at a constant agitation rate of 800 rpm), which generated dissolved oxygen concentration (DO) higher than 40%, were found the best for citric acid biosynthesis from glycerol. An increase in agitation rate (higher than 800 rpm) and aeration rate (higher than 0.36 vvm) had no impact on DO and citric acid production. The highest citric acid concentration (92.8 g/L) and yield (0.63 g/g) were obtained with Wratislavia 1.31 strain at 0.24 vvm. The highest volumetric citric acid production rate (1.15 g/Lh) and specific citric acid production rate (0.071 g/gh) were reached at 0.48 vvm.     

Effect of carbon source and aeration rate on broth rheology and fungal morphology during red pigment production by Paecilomyces sinclairii in a batch bioreactor

The influence of carbon source and aeration rate on fermentation broth rheology, mycelial morphology and red pigment production of Paecilomyces sinclairii was investigated in a 5-l stirred-tank bioreactor. The characteristics of P. sinclairii grown on starch and on sucrose medium were comparatively studied: the specific growth rate in sucrose medium (0.04 h(-1)) was higher than that in starch medium, whereas the specific production rate of red pigments (0.04 gg(-1)d(-1)) was favorable in starch medium. P. sinclairii grown in sucrose medium were highly branched and showed longer hyphal lengths than that in starch medium. The consistency index (K) in sucrose medium was markedly higher than that in starch medium due to higher cell mass, while the higher values of flow behavior index (n) were indicated at the late stationary phase in starch medium. The aeration rate was varied within the ranges from 0.5 to 3.5 vvm while running the fermentation at mild agitation of 150 rpm using sucrose as the carbon source. The maximum biomass concentration of P. sinclairii was about 33 gl(-1) with an aeration rate of 1.5 vvm, whereas the maximum yield of red pigment production (4.73 gl(-1)) was achieved with 3.5 vvm. The highly branched cell morphology appeared at 1.5 vvm and the highly vacuolated cell morphology was observed in a high aeration rate (3.5 vvm). There was no significant variance in rheological parameters (K and n) between culture broths from different aeration conditions.     

Optimization of physical parameters for exo-biopolymer production in submerged mycelial cultures of two entomopathogenic fungi Paecilomyces japonica and Paecilomyces tenuipes

AIMS: In the present study, two different optimization techniques were used to determine the suitable operating parameters for exo-biopolymer production in submerged mycelial cultures of two entomopathogenic fungi Paecilomyces japonica and Paecilomyces tenuipes. METHODS AND RESULTS: First, the rotating simplex method, a nonstatistical optimization technique, was employed to obtain the best combination of physical parameters (viz. pH, agitation intensity, aeration rate) for maximum exo-biopolymer production by P. japonica in a batch bioreactor. The optimal combination was determined to be a pH of 8.06, an aeration of 3 vvm, without any impeller agitation, producing a 17-time increase in exopolymer production (34.5 g l(-1)) when compared with that achieved in unoptimized flask cultures. Second, the uniform design method, a statistical optimization technique, was employed to determine the best operating parameters for submerged culture of P. tenuipes. The optimal combination for mycelial growth was determined to be a pH of 4.88, an aeration of 2 vvm and an agitation of 350 rpm, while a pH of 4, an aeration of 2 vvm and an agitation of 150 rpm was best for exo-biopolymer production. CONCLUSIONS: The exo-biopolymer production in P. japonica optimized by the rotating simplex method was strikingly improved (max. 34.5 g l(-1)), and the exo-biopolymer production in P. tenuipes optimized by the uniform design method was also significantly increased (max. 3.4 g l(-1)). SIGNIFICANCE AND IMPACT OF THE STUDY: The successful application of these two different optimization techniques in this study implies that these methods are worthy of applying to other fermentation systems for the production of bioactive mycelial biomass and exo-biopolymers in liquid culture of higher fungi.     

Fed-batch fermentation to produce oligonucleotides from Kluyveromyces marxianus grown on whey

Oligonucleotides (ON) extracted from yeasts are used as antiviral agents, immunostimulators, and flavour enhancers. Fed-batch fermentation of cheese whey by Kluyveromyces marxianus was carried out to produce high biomass yields to extract ON. K marxianus was grown for 20 h in medium containing 5% (w/v) dehydrated whey, at 30°C (pH 4.5), with agitation (350 rpm), and under aeration (1.0–2.0 vvm). After 20 h, media containing 10–15% (w/v) of dehydrated whey were added at different flow rates (180–230 ml/h). Samples were analyzed at 6–8 h intervals for cell count, lactose consumption, and ethanol production. Maximum production of biomass (28.13 g/l), yield (0.58 g/g), productivity (2.42 g/l per h), and specific growth rate (0.63 1/h) were obtained when medium containing 15% (w/v) of whey was added at 180 ml/h under 2 vvm aeration. Fed-batch fermentation converted 95% of whey lactose into biomass.     

Production of carbonyl reductase by Geotrichum candidum in a laboratory scale bioreactor

Fungal fermentation is very complex in nature due to its nonlinear relationship with the time, especially in batch culture. Growth and production of carbonyl reductase by Geotrichum candidum NCIM 980 have been studied in a laboratory scale stirred tank bioreactor at different pH (uncontrolled and controlled), agitation, aeration and dissolved oxygen concentration. The yield of the process has been calculated in terms of glucose consumed. Initial studies showed that fermenter grown cells have more than 15 times higher activity than that of the shake flask grown cells. The medium pH was found to have unspecific but significant influence on the enzyme productivity. However, at controlled pH 5.5 the specific enzyme activity was highest (306U/mg). Higher agitation had detrimental effect on the cell mass production. Dissolved oxygen concentration was maintained by automatic control of the agitation speed at an aeration rate of 0.6 volume per volume per minute (vvm). Optimization of glucose concentration yielded 21g/l cell mass with and 9.77x10(3)U carbonyl reductase activity/g glucose. Adaptation of different strategies for glucose feeding in the fermenter broth was helpful in increasing the process yield. Feeding of glucose at a continuous rate after 3h of cultivation yielded 0.97g cell mass/g glucose corresponding to 29.1g/l cell mass. Volumetric oxygen transfer coefficient (K(L)a) increased with the increasing of agitation rate.     

Processing characteristics of submerged fermentation of Antrodia cinnamomea in airlift bioreactor

Three 5-L airlift bioreactors including airlift reactor with solid draft tube (ALs), airlift reactor with net draft tube (ALn) and bubble column reactor (BC) were investigated for their suitability for cultivating Antrodia cinnamomea, and a stirred tank reactor (ST) was used for comparison. Results indicated that after 7 days fermentation, ALs yielded the highest mycelium content (313 mg/100 mL) and had the lowest dissolved oxygen in the broth. Among different aeration rates (0.025, 0.05, 0.1, 0.5, 1 vvm) used during cultivation of A. cinnamomea in ALs, the aeration rate 0.1 vvm resulted in a volumetric oxygen transfer coefficient of 10.8 h⁻¹ and produced the highest mycelium content. When the optimal conditions were used for the fermentation of A. cinnamomea in an industrial 500-L ALs, the mycelium content in the broth reached 542 mg/100 mL in 28 days. The IC₅₀ values of the ethanol extracts of A. cinnamomea mycelium cultivated in 5-L and 500-L ALs for 28 days were 23 and 17 μg/mL, respectively, for hepatocellular carcinoma cells HepG2. And after 42 days cultivation in 500-L ALs, the IC₅₀ value of the mycelium ethanol extract was reduced to 10 μg/mL.