碱性过氧化氢预处理后汽爆玉米秸秆半同步糖化发酵生产乙醇

为了实现纤维素乙醇生产的"三高"(高浓度、高转化率和高发酵效率)指标,以复合预处理处理后的玉米秸秆为基质,探究其半同步糖化发酵工艺过程。通过对其高底物浓度预酶解过程特性考察,确定其最佳预酶解工艺为:在加酶量30 FPU/g干基质和50℃下,以15.6%(w/v)为起始基质浓度,在酶解12 h时补加相当于20%(w/v)初始基质浓度的干物料后继续酶解24 h。在最佳预酶解工艺基础上,探究了培养基成分和培养条件对乙醇发酵的影响,确定了发酵过程工艺:酵母提取物16 g/L、接种龄20 h、接种量0.6 g干菌体/L、发酵温度39℃和PEG4000 0.01 g/g干基质。在最佳的半同糖化发酵工艺下,发酵24 h后,乙醇产量达73.75 g/L,发酵效率为3.07 g/(L·h),转化率为61%。结果表明通过补料半同步糖化发酵过程可以实现高浓度和高发酵效率双重目标,这有利于推进纤维素乙醇生产的工业化发展。     

不同初始葡萄糖浓度乙醇发酵过程研究

对酿酒酵母GGSF16不同初始葡萄糖浓度乙醇发酵进行研究,旨在了解不同初始葡萄糖浓度乙醇发酵过程,得到乙醇分批发酵的最适初始葡萄糖浓度。通过Logistic方程对乙醇发酵过程进行拟合。基于得到的拟合方程,对乙醇发酵过程中葡萄糖消耗、酵母生长及乙醇生成的速率进行比较。结果表明,随着初始葡萄糖浓度升高,发酵过程中葡萄糖消耗、酵母生长及乙醇生成的速率降低以及达到最大速率的时间滞后,从发酵结果综合比较乙醇浓度、葡萄糖利用率及发酵效率,初始葡萄糖浓度为286.5g/L的乙醇发酵结果较为理想,最终乙醇浓度达到133.14 g/L,葡萄糖利用率为99.07%,对总糖的发酵效率为90.95%。     

氮源对酿酒酵母GJ2008不同糖浓度甘蔗汁酒精分批发酵的影响

研究了不同糖浓度下氮源对酿酒酵母GJ2008甘蔗汁酒精发酵的影响,旨在为高浓度甘蔗汁酒精发酵提供研究基础。将2 g/L尿素加入150 g/L、200 g/L、250 g/L、300 g/L和350 g/L总糖质量浓度甘蔗汁培养基中,以对应糖浓度未添加氮源组为对照组,通过分析细胞生长、糖代谢和乙醇生成来探究氮源如何影响甘蔗汁酒精发酵。结果表明：与未添加氮源相比,氮源加快了发酵速度,发酵周期最高缩短为18 h,糖消耗速率和乙醇生成速率最大分别提高了55%和96%;使酒精发酵更彻底,总糖含量最高减少了40.42 g/L;增加了目的产物,乙醇含量最高提升了28.4%。说明氮源有效地促进了甘蔗汁酒精发酵,加强了酵母的无氧呼吸途径。     

桑葚果酒分批发酵动力学研究

以桑葚汁为原料,探讨果酒发酵过程中菌体生长、产物生成和底物消耗变化规律,利用Logistic模型方程拟合菌体生长、产物生成、基质消耗曲线,建立发酵动力学模型。结果表明,当发酵液初始含糖量为200g/L时,接种5%活化酵母,28℃发酵100h后,残糖含量降为3.86g/L,酵母数量增长为2.83×108 CFU/mL,乙醇含量达到9.01%,菌体生长、产物生成、基质消耗的动力学模型拟合度良好,模型R2分别为0.974,0.988,0.991,模型能较好地反映和预测桑葚果酒发酵变化的过程。     

有机酸对Actinobacillus succinogenes厌氧发酵过程的抑制作用

通过在发酵培养基中分别添加不同浓度的丁二酸、甲酸和乙酸,考察了3种有机酸对菌体生长及代谢产物积累的影响。结果表明,在初始葡萄糖浓度为40 g/L厌氧发酵产丁二酸体系中,甲酸抑制作用最强,乙酸次之,丁二酸无明显抑制作用。当甲酸和乙酸总浓度超过13.70 g/L时,菌体开始衰亡。利用膜循环生物反应器在发酵过程甲酸和乙酸总浓度达到13.70 g/L时移出部分抑制性代谢产物,有效地降低了有机酸对A.succi-nogenes NJ113生长代谢的抑制作用,丁二酸生产强度达1.70 g/(L.h),比分批发酵提高了17.2%。     

促进酵母菌乙醇发酵新方法

在发酵培养基中添加固态基质,研究不同固态基质对酵母菌乙醇发酵的促进作用。结果表明：在培养基中分别添加2g/100mL 的麦秸杆、花生壳、稻壳和锯末,可使发酵液中乙醇质量浓度提高了15.5%～24.8%。在4种不同固态基质中,稻壳对酵母菌乙醇发酵的促进作用最显著。以稻壳作为固态基质,确定了添加固态基质条件下酵母菌乙醇发酵的最适条件为：稻壳2.5g/100mL、初糖12g/100mL、温度30℃、发酵时间48h。在适宜的发酵条件下,发酵液中乙醇质量浓度可达到51.8g/L,为理论产率的92.7%。     

产脂肪酶海洋酵母Bohaisea-9145批式发酵动力学研究

以从渤海海域海泥中分离获得一株产脂肪酶海洋酵母Bohaisea-9145为实验菌株,为认识其发酵机理并指导发酵工艺设计,利用批式发酵方法研究该酵母菌体生长和菌体产酶情况.该酵母菌发酵类型为生长非关联型,发酵溶氧浓度最佳为30％±2％,当限制性基质葡萄糖浓度达到2.2772g/L时细胞生长速率最大,通过数学推导和批式发酵结果建立了海洋酵母菌体生长和产脂肪酶动力学模型.     

葡萄糖浓度对产丁醇芽孢杆菌菌体生长与代谢特性的影响

研究了在兼性厌氧条件下初始葡萄糖浓度对产溶剂芽孢杆菌(Bacillus sp.)C2菌株菌体生长和代谢特性的影响。结果表明:5%初始葡萄糖浓度下菌体的生长速率低于低糖浓度的处理;随发酵产物浓度升高,部分菌体变长;前芽孢及成熟芽孢数量在发酵过程中变化不明显。2%、4%和5%初始糖浓度下,总溶剂产量分别在发酵的72、54和90 h达到最高值,为5.49、11.96和18.4 g/L,其中丁醇占70%,总溶剂的产率分别为0.309、0.303和0.366 g/g。3%初始糖浓度发酵时,发酵于36 h前停止,溶剂产量仅为2.4 g/L。     

NH_4~+对合成气乙醇发酵过程的影响及其酶学机理

为研究合成气厌氧乙醇发酵中合成气杂质组分NH_3对发酵过程的影响,实验通过考察发酵培养基内不同初始浓度的NH~+_4对菌株A-fm4,Clostridium ljungdahlii和Clostridium autoethanogenum DSM10061利用生物质合成气发酵乙醇的影响,证实低浓度的NH~+_4可促进菌体生长和乙醇发酵,当其浓度高于9.35 mmol/L时,菌体生长和乙醇发酵随其浓度的增大而抑制显著。对菌株在菌体生长期和乙醇/乙酸发酵期内4种关键酶的活性研究表明,氢化酶(H_2ase)、一氧化碳脱氢酶(CODH)、乙醇脱氢酶(ADH)和乙酸激酶(ACK)均受高浓度(149.6 mmol/L)NH~+_4抑制,且菌体生长期的酶活水平均高于发酵期的值。这说明在低浓度NH~+_4下可促进还原力的产出而利于乙醇发酵,而较高浓度NH~+_4抑制代谢途径,致使菌体生长和乙醇发酵受阻。菌株C.ljungdahlii和C.autoethanogenum DSM10061的K_i值分别为208.13 mmol/L和240.37 mmol/L,耐铵能力较强,可作为未来耐铵菌株的驯化提供材料,为降低工业生产成本和减少合成气净化工艺工序奠定基础。     

有机酸对Actinbacillus succinogenes厌氧发酵过程的抑制作用

通过在发酵培养基中分别添加不同浓度的丁二酸、甲酸和乙酸,考察了3种有机酸对茵体生长及代谢产物积累的影响.结果表明,在初始葡萄糖浓度为40 g/L厌氧发酵产丁二酸体系中,甲酸抑制作用最强,乙酸次之,丁二酸无明显抑制作用.当甲酸和乙酸总浓度超过13.70 g/L时,菌体开始衰亡.利用膜循环生物反应器在发酵过程甲酸和乙酸总浓度达到13.70 g/L时移出部分抑制性代谢产物,有效地降低了有机酸对A.succinogenes NJ113生长代谢的抑制作用,丁二酸生产强度达1.70 g/(L·h),比分批发酵提高了17.2%.     

Robust industrial Saccharomyces cerevisiae strains for very high gravity bio-ethanol fermentations

The application and physiological background of two industrial Saccharomyces cerevisiae strains, isolated from harsh industrial environments, were studied in Very High Gravity (VHG) bio-ethanol fermentations. VHG laboratory fermentations, mimicking industrially relevant conditions, were performed with PE-2 and CA1185 industrial strains and the CEN.PK113-7D laboratory strain. The industrial isolates produced remarkable high ethanol titres (>19%, v/v) and accumulated an increased content of sterols (2 to 5-fold), glycogen (2 to 4-fold) and trehalose (1.1-fold), relatively to laboratory strain. For laboratory and industrial strains, a sharp decrease in the viability and trehalose concentration was observed above 90 g l?1 and 140 g l?1 ethanol, respectively. PE-2 and CA1185 industrial strains presented important physiological differences relatively to CEN.PK113-7D strain and showed to be more prepared to cope with VHG stresses. The identification of a critical ethanol concentration above which viability and trehalose concentration decrease significantly is of great importance to guide VHG process engineering strategies. This study contributes to the improvement of VHG processes by identifying yeast isolates and gathering yeast physiological information during the intensified fermentation process, which, besides elucidating important differences between these industrial and laboratory strains, can drive further process optimization.     

“酒精沼气双发酵耦联工艺”中硫化物对酒精发酵的影响

"酒精沼气双发酵耦联工艺"中硫化物会对酒精发酵产生抑制,不利于工艺的稳定运行。与对照相比,pH 4.0,24 mmol/L的硫化物使酒精发酵时间从48 h延长至318 h,酒精产量由90.73 g/L下降至82.28 g/L,酵母数量由3.78×108/mL下降至2.20×108/mL,甘油产量由6.99 g/L上升至11.02 g/L。甘油产量上升是硫化物存在时酒精产量下降的原因之一。硫化物对酒精发酵的抑制性随添加时间的推迟而减弱,这是因为在酒精发酵过程中,硫化物会以H2S的形式随着CO2一起从发酵液逸出。pH 4.0时,硫化物对酒精发酵的临界抑制浓度为1.2 mmol/L。     

L-乳酸菌的选育及在酒糟基质中的培养

从市售酸乳、泡菜中筛选得到产L-乳酸细菌,通过NTG诱变选育和摇瓶发酵试验,选出两株利用葡萄糖较好的菌株m-58和m-16,以玉米浓醪酒糟清液为基质对2株乳酸细菌进一步驯化培养,得出m-58菌株,更能较好地发酵玉米酒：糟清液,产生乳酸,m-58菌株在48h发酵含糖63gm的玉米浓醪酒糟清液产生50gm的L-乳酸,m-58菌株适合用于发酵玉米酒糟产乳酸。     

Effects of magnesium ions on both VHG batch and continuous fruit wine fermentations

In Poland, fruit wines or aromatized fruit wines are semi‐sweet or sweet and contain approximately 15–16% (v/v) ethanol. Their production can be classified as a very high‐gravity (VHG) fermentation. Magnesium has a beneficial effect on VHG fermentations as it protects the yeast cells against ethanol, osmotic and temperature stress. The effect of the magnesium concentration in an apple must, containing 32% sugars, on the fermentative parameters of batch and continuous fermentations was assessed. In the batch process, a magnesium concentration of ~8.5 mg/L resulted in decreased the ethanol production in comparison to a magnesium concentration of ~250, 490 and 970 mg Mg²⁺/L. The highest amount of Mg also caused a metallic taste. A continuous fermentation was carried out for 2.5 months in a four‐column packed‐bed fermentor. The medium contained ~50, 250 and 490 mg Mg²⁺/L and the yeast was immobilized on foam glass. During the continuous fermentation, no differences at p ≤ 0.05 in terms of fermentative parameters were seen with magnesium additions. The same beginning amount of magnesium ions in the medium led to a similar use of this element, both in batch and in continuous fermentation. The more Mg²⁺ that was present in the medium, the more Mg²⁺ was used by the yeast. The results suggest that the minimal dose of magnesium, under the described conditions, is 50 mg/L, corresponding to the amount of Mg in the medium prepared using concentrated apple juice and tap water. This finding has industrial significance, as Polish wine companies prepare their fruit musts using tap water. Copyright © 2014 The Institute of Brewing & Distilling     

发酵木糖高产乙醇休哈塔假丝酵母突变株的选育

木糖的乙醇发酵是利用木质纤维原料生产乙醇的关键环节。休哈塔假丝酵母是木糖发酵性能较好的天然酵母之一。研究中对Candida shehatae CICC1766进行了紫外诱变和离子注入诱变,力求选育出发酵木糖产乙醇能力强的假丝酵母。先将其进行紫外诱变,得到的突变株S28在木糖添加量为60g/L的条件下乙醇产量为2364g/L,相比原始菌株提高1498%,乙醇得率达到0394g/g(乙醇/木糖)。再对S28进行氮离子注入诱变,得到的突变株SY58乙醇产量为2508g/L,相比S28提高609%,乙醇得率为0418g/g(乙醇/木糖),达到理论得率的908%。进而对SY58菌株进行了5L罐发酵实验,乙醇产量达到2504g/L,得率为0417g/g(乙醇/木糖),同摇瓶发酵结果基本相同,并且发酵时间由原来的72h缩短到52h。     

丙酮丁醇梭菌发酵条件优化研究

以P2培养基为基础组分,分别通过改变初始葡萄糖浓度、初始酵母膏浓度以及初始pH值,研究这3个单因素对丁醇发酵的影响,确定了培养基的较佳条件:初始葡萄糖浓度60g/L、初始酵母膏浓度3g/L、初始pH值6.8.此外,采取接种量5％、发酵温度37℃、发酵时间72h,可使总溶剂浓度(丁醇、丙酮、乙醇)达到13.52g/L,其中丁醇、丙酮、乙醇浓度分别为8.83g/L、3.90g/L和0.79g/L,丁醇比例为65.31％.糖丁醇转化率为21.1％(平均值),糖总溶剂转化率为31.3％(平均值).     

琥珀酸发酵过程中的产物抑制特征及树脂吸附原位分离的研究

研究了使用Actinobacillus succinogenes菌种以葡萄糖为底物,发酵生产琥珀酸过程中的产物抑制特征,及使用原位分离技术(ISPR)来消除产物抑制现象,以提高底物转化率。研究发现,该菌种的生长与发酵呈现出明显的非偶联特征,在菌体生长进入稳定期(30 h培养)后,开始大量合成产物琥珀酸。当发酵液中琥珀酸浓度高于25 g/L时,开始出现明显的产物抑制作用,底物转化效率逐渐降低。通过模拟发酵液筛选出了对琥珀酸有较强吸附的D301T、D301R、D303树脂,并通过真实发酵筛选出了对发酵体系无毒性的D301R树脂。最后通过5L发酵罐,对树脂吸附原位分离发酵进行验证,在接种后30h将树脂D301R以40 g/L的量添加入5L发酵罐中,至发酵终点琥珀酸产量达到49.46 g/L(底物葡萄糖60 g/L),底物葡萄糖转化率达到82.43%,相比普通发酵过程,底物转化率提高了21%。     

凝集型酵母酒精发酵的研究

通过Saccharomyces 1～5号菌株间歇发酵试验发现,间歇通气发酵与摇床发酵方式的发酵速率远高于静置发酵,摇床发酵的糖醇转化率48h超过80%。说明适量通风可使酵母菌在反应器中保持高密度和高活性,进而加快反应的进行,并提高糖醇转化率,尤其是在发酵前期可以使酵母菌快速增殖建立优势环境。在二级反应器中的连续发酵试验中,当稀释速率为0.05/h时,流出末级反应器的发酵液酒精浓度达到77.4g/L,糖醇转化率达到89.93%,反应器发酵速率为3.87g/(L.h),残余还原糖浓度为8.2 g/L。     

The Dynamic Changes of Proton Efflux Rate in Saccharomyces pastorianus Strains During High Gravity or Very High Gravity Brewing

The changes in the proton efflux rate (PER) during fermentation of normal gravity (NG), high gravity (HG) and very high gravity (VHG) wort by a lager yeast (Saccharomyces pastorianus) were monitored using an optimized PER test method. The values of the proton efflux rate in S. pastorianus decreased with increasing initial wort gravity. Moreover, the difference in the proton efflux rate values at the beginning of the fermentation was lower than at the end of fermentation from normal gravity to very high gravity brewing. These results demonstrated that the proton efflux rate in S. pastorianus was inhibited in the later stages of high gravity and very high gravity brewing. Furthermore, the changes of the proton efflux rate in S. pastorianus under the high ethanol concentration conditions appeared to depend on the concentration of ethanol in the fermentation liquid. A better negative correlation (P > 0.001, r = ?0.95) between the ethanol concentration at >4% (w/v) and the proton efflux rate was found. The changes of the proton efflux rate in the cells treated with exogenous ethanol confirmed that higher concentrations of ethanol could significantly inhibit proton efflux in S. pastorianus. This study offers a possible way to monitor and explain the performance of yeast in the complex environment of high gravity and very high gravity brewing.     

玉米秸秆稀酸水解液发酵生产纤维素乙醇的研究

该文系统考察了溶氧、初始pH值、培养温度、氮源以及玉米秸秆稀酸水解液中糠醛和乙酸对嗜鞣管囊酵母乙醇发酵的影响。结果表明,装液量75mL/250mL三角瓶、转速80r/min、初始pH值为5.5、培养温度30℃和酵母膏6g/L是嗜鞣管囊酵母乙醇发酵的较佳条件,乙醇产量可达到7.52g/L;糠醛和乙酸对嗜鞣管囊酵母细胞增殖、乙醇合成和底物消耗具有明显的抑制作用,且糠醛和乙酸同时存在于发酵培养基中会加剧抑制的产生。经菌种驯化改良后,嗜鞣管囊酵母G21增强了对秸秆稀酸水解液的适应性,实际乙醇得率由77.7%vol提高至89.4%vol。