连续发酵研究及其应用进展

连续发酵是目前发酵工程研究的方向之一。本文介绍了连续发酵应用概况、连续发酵的起点和稳态、连续发酵相关工艺、连续发酵的内在缺陷、新技术和新理论在连续发酵中的应用等。     

Synchronization affector of autonomous short-period-sustained oscillation of Saccharomyces cerevisiae

When the yeast Saccharomyces cerevisiae was grown under aerobic continuous culture, an autonomous shortperiod-sustained oscillation appeared. This oscillation was observed in concentrations of various extracellular and intracellular parameters, such as ethanol, acetate, glycogen, dissolved oxygen and intracellular pH. In this work the synchronization affecter of this oscillation was investigated. Ethanol was found not to be the synchronizer of the oscillation because a pulse of ethanol did not affect the phase or period of the oscillation. The oscillation was dependent on the aeration rate, i.e., the oscillation occurred only between 150 and 600 ml min⁻¹. However, the oxygen concentration did not influence synchronization as an upward shift in the oxygen concentration of the gas flow did not affect the sustainability of the oscillation. On the other hand, synchronization was stopped by an enhanced gas flow rate, keeping dissolved oxygen tension at the oscillatory condition, suggesting that synchronization was caused by a volatile compound in the culture. A stepwise increase in carbon dioxide concentration of the gas flow rate ceased synchronization, yet the oscillation seem to continue in each individual cell. Oscillatory behaviour of intracellular pH and carbon dioxide evolution rate showed a phase difference of 90 degrees. Based on these facts it is postulated that carbon dioxide, through the influence of its dissociation on intracellular pH, could be the synchronization affector of the autonomous short-period-sustained oscillation of S. cerevisiae.     

Production of an Alcoholic Beverage by Fermentation of Whey Permeate with Kluyveromyces fragilis II: Aroma Composition

Whey permeate was used for an alcoholic fermentation with Kluyveromyces fragilis (CECT 1123). The aim of the present study was the production of an alcoholic beverage of low alcoholic proof with acceptable concentrations of fusel alcohols. The effects of temperature and agitation on the concentration of volatile compounds was assayed in batch cultures. In addition, the production of acetaldehyde, ethyl acetate and fusel alcohols was studied in continuous culture because of interest in a continuous industrial process. Final concentrations of fusel alcohol were slightly lower at higher temperatures, while the specific production rate increased with temperature. Concentrations were suitable, in all cases, for a beverage. When agitation was assayed, an important increase in fusel alcohol concentrations was found at higher agitations. In continuous culture, the acetaldehyde, ethyl acetate and fusel alcohol concentrations were normal for an alcoholic beverage.     

不同玉米品种发芽过程中碳水化合物代谢变化的初步研究

以普通玉米(苏玉24号,SY-24)、糯玉米(紫花糯玉米,ZY)和甜玉米(京晶3号,TY)为试材,研究了不同玉米品种的组分差异及不同发芽阶段生理生化和碳水化合物组成的变化.结果表明:不同品种玉米之间存在组分差异,SY-24的千粒重和直链淀粉含量最高,ZY中未检测到直链淀粉;ZY的水分、还原糖、可溶性糖、Mg、Na和Ca的含量最高;TY中的类胡萝卜素、可溶性蛋白、游离氨基酸、灰分、粗脂肪、Zn和K含量最高.SY-24中未检出Ca;TY和SY-24中Fe含量没有显著差异(P＞0.05),但均显著高于ZY(P＜0.05),分别是ZY中铁含量的4.69和1.04倍.在发芽过程中,芽长、发芽率、呼吸强度逐渐升高,干物质含量逐渐降低;淀粉酶活力而逐渐增加,β-淀粉酶活力显著高于α-淀粉酶活力(P＜0.05);在淀粉酶作用下,淀粉含量逐渐降低,淀粉颗粒逐渐变小,ZY中没有检测到直链淀粉,SY-24和TY直链淀粉含量随发芽时间延长呈先增加后降低,并分别在第24h和第36h达到最大值,分别是未发芽的3.10倍和1.46倍;可溶性糖在发芽过程中呈现波动变化;ZY和SY-24中还原糖含量逐渐增加;TY中还原糖含量呈现先降低后增加的趋势,在发芽地12h达到最低,与未发芽相比降低了15.44％.     

秋水仙碱处理对采后莲雾果实在冷藏期间品质、活性氧代谢和能量代谢的影响

目的：研究0.01%秋水仙碱处理对采后莲雾果实在冷藏期间生理品质、活性氧代谢和能量代谢的影响,探讨秋水仙碱影响采后莲雾的衰老机制。方法：分别用0、0.01%的秋水仙碱溶液浸泡莲雾果实15 min,于4 ℃贮藏,检测果实品质、活性氧代谢和能量代谢的变化。结果：秋水仙碱处理可以抑制贮藏期间絮状绵软指数的上升,第4天之后效果显著（P＜0.05）,处理后的果实质量损失率整个贮藏期间显著低于对照组（P＜0.05）;秋水仙碱处理可以减缓超氧化物歧化酶（SOD）活性的下降,抑制过氧化氢酶（CAT）活性高峰的出现,保持较低CAT活性,显著提高贮藏后期第8～12天过氧化物酶（POD）活性（P＜0.05）;同时可以保持较高琥珀酸脱氢酶（SDH）和细胞色素C氧化酶（CCO）活性,处理组的SDH活性在第4、8、12天显著高于对照组（P＜0.05）,CCO活性在第2、6、8天显著高于对照组（P＜0.05）;秋水仙碱处理还可以减缓贮藏后期ATP含量和能荷水平的下降,与对照组有显著差异（P＜0.05）。结论：0.01%的秋水仙碱处理能显著延缓采后莲雾果实絮状绵面积的增加;采后莲雾果实絮状绵软面积与能荷水平呈显著负相关性（r=－0.793,P＜0.05）,能量亏缺会加剧莲雾果实衰老;能荷水平与活性氧代谢指标H2O2含量呈显著负相关（r=－0.766,P＜0.05）,与SOD活性呈显著正相关（r=0.802,P＜0.05）,能量代谢会影响活性氧代谢;秋水仙碱主要依靠调节能量代谢起作用。     

玉米发芽过程中碳水化合物代谢变化的研究

以苏玉24号玉米品种为试材,研究不同发芽阶段玉米的主要生理生化变化和碳水化合物组成变化。结果显示：随着发芽时间的延长,干物质含量减少,芽长和发芽率均呈现不同程度的增加,呼吸强度整体呈上升的趋势,可溶性蛋白在发芽60h达到最低,与未发芽相比降低了39.47%;淀粉酶活力逐渐增大,α-淀粉酶、β-淀粉酶和总淀粉酶活力在发芽60h时分别是未发芽玉米的4.74、16.82倍和14.41倍,在发芽108h时分别是未发芽玉米的18.33、69.77倍和59.58倍;在淀粉酶的作用下,淀粉含量总体呈下降的趋势,60h达到最小值,比未发芽玉米降低了12.62%;直链淀粉含量总体也呈下降的趋势,发芽60h后比未发芽降低了3.19%,而还原糖、可溶性糖逐渐增大,在发芽72h达到最大值,分别是未发芽玉米的4.69倍和6.88倍;同时DE值(dextrose equivalent value)先增大后减小,在发芽36h后变化显著(P＜0.05),并在发芽84h达到最大值,是未发芽玉米的13.71倍。各指标相关性表明玉米发芽过程中主要生理变化对碳水化合物的组成有很大影响。     

物理活性包装对香菇贮藏品质、呼吸及能量代谢的影响

为研究普通PE包装（CK）和物理活性包装（Physically active packaging,PA）对采后香菇贮藏品质、呼吸及能量代谢的影响,以香菇‘808’为实验材料,将其置于（4±1）℃,相对湿度（90±5）%条件下贮藏12 d,每隔3 d测定其感官品质、失重率、硬度、可溶性固形物含量、可溶性蛋白含量、呼吸速率、呼吸及能量代谢关键酶活性、能量物质及能荷等相关指标。结果表明,PA处理延缓了香菇感官品质的劣变进程,抑制香菇失重率的增加,减缓香菇硬度、可溶性固形物和可溶性蛋白含量的下降,降低香菇呼吸强度,延缓其呼吸峰值的出现。进一步研究表明,PA处理下香菇能维持较高的细胞色素C氧化酶（cytochrome C oxidase,CCO）和苹果酸脱氢酶（malate dehydrogenase,MDH）酶活性水平,抑制了磷酸葡萄糖异构酶（glucose-6-phosphate isomerase,PGI）、琥珀酸脱氢酶（succinate dehydrogenase,SDH）和丙酮酸脱氢酶（Pyruvate dehydrogenase,PDH）酶活性的快速升高。同时,PA处理还能抑制香菇ATP、ADP的降解,维持较高的能荷水平。相关性分析结果显示,香菇的感官品质与硬度、可溶性固形物、MDH、ATP、能荷呈现极显著性正相关（P<0.01）,与可溶性蛋白、ADP呈显著性正相关（P<0.05）,与失重率、AMP呈现极显著性负相关（P<0.01）,表明在物理活性包装条件下,香菇贮藏品质与能量水平紧密相关。因此,物理活性包装能有效抑制香菇采后呼吸及能量代谢,维持香菇的贮藏品质,减少经济损失。     

超声处理对鹿茸菇贮藏品质的影响

为探究超声处理对鹿茸菇贮藏品质的影响,本实验以新鲜鹿茸菇为试材,经超声(35 kHz、300 W)处理10 min后,测定鹿茸菇感官品质及能量代谢相关酶等相关指标。结果表明,超声处理相较于对照组可以维持鹿茸菇较高的亮度,并保持较高的总蛋白、抗坏血酸、谷胱甘肽含量,提高总超氧化物歧化酶活力,明显降低褐变程度。与对照组相比,贮藏期间超声处理组ATP、还原型烟酰胺腺嘌呤二核苷酸磷酸(nicotinamide adenine dinucleotide phosphate,NADPH)、氧化型NADPH(oxidized NADPH,NADP⁺)含量处于较高水平,6-磷酸葡萄糖脱氢酶、H⁺K⁺-ATPase、Na⁺K⁺-ATPase、Ca²⁺Mg²⁺-ATPase活力较高,表明超声处理延缓了鹿茸菇品质劣变现象。因此,超声保鲜可以为采后食用菌保鲜提供参考。     

红肉蜜柚果实采后贮藏过程中果皮与汁胞能量代谢的差异

为了研究红肉蜜柚果实采后贮藏过程中果皮与汁胞能量代谢的差异,对比2种处理方式(常温25?℃贮藏(对照)、8?℃冷藏)对果实3个部位(汁胞、白皮层和外果皮)的水分质量分数、丙二醛(malondialdehyde,MDA)含量、能量相关物质含量、相关酶活力、能荷(energy charge,EC)和汁胞可溶性固形物质量分数...     

褪黑素对青椒低温贮藏品质及能量代谢影响

为研究褪黑激素对采后青椒果实贮藏品质和能量代谢的影响,本研究以青椒为材料,研究了100、200和300 μmol/L浓度褪黑素对9 ℃下贮藏的青椒果实品质及能量代谢的影响。结果表明,褪黑素处理能有效地降低青椒果实腐烂率,减缓青椒果实硬度的下降,其中,200 μmol/L褪黑素的处理效果最好;此外,褪黑素能推迟青椒果实辣椒碱含量、叶绿素含量的下降,维持较低的丙二醛（MDA）含量,抑制青椒三磷酸腺苷（ATP）、二磷酸腺苷（ADP）和腺嘌呤核苷酸（AXP）的降解,促进一磷酸腺苷（AMP）含量的积累,维持了较高的能荷水平。褪黑素也能维持青椒中的较高的琥珀酸脱氢酶（SDH）活性、细胞色素C氧化酶（CCO）活性、氢离子ATP酶（H⁺-ATPase）酶活性和钙离子ATP酶（Ca²⁺-ATPase）酶活性。相关性分析表明,青椒的ATP、ADP、AXP、能荷、H⁺-ATPase、Ca²⁺-ATPase活性与腐烂率呈显著负相关（P<0.05）,与辣椒碱和叶绿素含量呈显著正相关（P<0.05）,并且青椒的ATP、ADP、AMP、AXP、能荷和H⁺-ATPase、Ca²⁺-ATPase活性互相之间均呈现显著正相关（P<0.05）,表明褪黑素处理能够说明采后青椒贮藏期品质与能量水平紧密相关。研究结果可为褪黑素在控制采后青椒贮藏品质方面的应用提供技术参考。     

冷藏期间苹果果实能量和NADP-苹果酸酶及基因表达的变化

为研究冷藏期间苹果果实能量水平和NADP-苹果酸酶（NADP-ME）及基因表达的变化情况,本研究以‘长富2’苹果果实为实验材料,定期测定果实硬度、可溶性固形物等品质指标和能量相关物质三磷酸腺苷（ATP）、二磷酸腺苷（ADP）、磷酸腺苷（AMP）含量和能荷变化及NADP-ME、琥珀酸脱氢酶（SDH）活性。结果显示,冷藏期间,‘长富2’果实ATP含量贮藏前60 d下降,而后恢复到贮藏初期水平,ADP和AMP贮藏前60 d稍有降低后,随时间延长显著增加;NADP-ME和琥珀酸脱氢酶（SDH）活性均随贮藏时间延长逐渐降低;辅酶Ⅱ（NADP+）和还原型辅酶Ⅱ（NADPH）含量在贮藏前120 d先增加后下降,与能荷变化相似;Mdcy ME1-Mdcy ME3基因表达虽在时间上有一定差异,但表现出相似的先增加后下降的趋势。冷藏期间苹果果实能量水平和利用效率发生了改变,且能量水平与NADP-ME活性及其基因表达在统计学上存在相关性。      

客家娘酒发酵过程中的糖代谢

采用柱前衍生高效色谱法测定客家娘酒发酵过程中糖类物质的含量,监控发酵过程中糖类物质的动态变化规律。在此基础上,研究客家娘酒糖代谢过程的影响因素,使用相关分析研究红曲用量、麦曲用量、主酵时间及主酵温度对糖类物质含量的影响。结果表明:在发酵过程中,葡萄糖的含量最高,其次是异麦芽糖和麦芽糖,含量最低的为潘糖,在后酵阶段末期潘糖几乎检测不出。异麦芽糖与4种发酵参数均呈显著正相关(P<0.01);异麦芽三糖含量与红曲用量呈显著负相关(P<0.01),与其他3种参数呈显著正相关(P<0.01);麦芽糖含量均呈显著负相关(P<0.01);葡萄糖含量与麦曲用量、主酵时间呈显著负相关(P<0.01),与其他因素呈显著正相关(P<0.01)。     

Isomaltooligosaccharide synthesised from rice starch and its prebiotic properties in vitro

The isomaltooligosaccharides (IMOs) were produced from rice starch with a maximum conversion yield of 84% and had a concentration of 372.5 mg mL^?1. Compositions of IMO consisted of 26.7% isomaltohexaose (DP6), 16.2% isomaltotetraose (DP4), 19.6% d ‐panose (DP3), 21.4% and isomaltose (DP2) and had a dietary fibre content of 1.1%. In vitro (consisted of three vessels) fermentation of instant Sang‐Yod rice porridge (ISYRP) mixed with IMO showed a slight increase in beneficial bacteria, bifidobacteria and lactobacilli. On the other hand, the pathogenic bacteria, clostridia and bacteroides were decreased (P < 0.05). The highest prebiotic index (PI) was found in Vessel 1 (0.13). Butyric acid was found at the highest concentration on day 11 (75.1 mm ), and it was decreased at day 21 (63.4 mm ) in Vessel 1. In conclusion, the ISYRP mixture of IMO was showed a good preference in prebiotic properties.     

Increased ethylene biosynthesis elevates incidence of chilling injury in cold‐stored ‘Amber Jewel’ Japanese plum (Prunus salicina Lindl.) during fruit ripening

Mature ‘Amber Jewel’ Japanese plum fruit were stored at 0 or 5 °C for 3 and 6 weeks to investigate their effects on ethylene (C₂H₄) biosynthesis during ripening at ambient temperature in the development of chilling injury (CI) and fruit quality. CI (internal breakdown and browning) and fruit softening were higher during ripening, in the fruit stored at 5 °C than 0 °C, irrespective of storage period (SP). C₂H₄ production and activities of 1‐aminocyclopropane‐1‐carboxylic acid synthase (ACS) and 1‐aminocyclopropane‐1‐carboxylic acid oxidase (ACO) enzymes, and 1‐aminocyclopropane‐1‐carboxylic acid (ACC) content were higher during ripening in fruit stored at 5 °C than 0 °C. The fruit stored at 5 °C also exhibited higher respiration rate and higher soluble solids concentration/titratable acidity ratio. In conclusion, increase in storage temperature and SP elevates the activities of ACS and ACO enzymes and consequently C₂H₄ production which leads to the development of CI in plum fruit with advancement of ripening.     

1-甲基环丙烯通过调控香菇能量代谢抑制其采后褐变

目的：研究1-甲基环丙烯（1-methylcyclopropene,1-MCP）处理对香菇褐变和能量代谢的影响,探讨香菇能量代谢与褐变的关联,为香菇采后保鲜提供一定的理论参考。方法：分别采用0.25、0.50、0.75 mg/L的1-MCP对香菇进行熏蒸处理,测定香菇采后色泽、呼吸和能量代谢相关酶活力。结果：1-MCP能够有效降低香菇菌盖的褐变度;且1-MCP处理后,香菇的呼吸作用得到抑制,呼吸强度降低;同时,1-MCP处理能抑制香菇多酚氧化酶（polyphenol oxidase,PPO）活力的增加;在1-MCP处理下,香菇在贮藏期间的能荷水平较高,子实体维持了较高的琥珀酸脱氢酶（succinate dehydrogenase,SDH）活力、细胞色素c氧化酶（cytochrome c oxidase,CCO）活力和腺嘌呤核苷三磷酸（adenosine triphosphate,ATP）酶活力。结论：1-MCP可以通过调节香菇的呼吸作用,降低PPO活力,维持子实体的能量水平和影响能量代谢相关酶活力,延缓香菇菌盖的褐变。