直肠菌群对两种抗性淀粉的体外发酵研究

分别以两种抗性淀粉为唯一碳源,对直肠菌群进行体外发酵。通过研究发现,发酵过程中两种培养基的pH呈逐渐下降的趋势;双歧杆菌属、乳杆菌属的数量呈上升趋势;肠球菌属和肠杆菌属的数量也能保持比较稳定的数量,而拟杆菌的数量在发酵中后期开始减少,但总厌氧菌数比较稳定,因此发酵过程中肯定有不同菌属的生长演替;两种碳源均能被肠道菌群利用产生短链脂肪酸,其中以丙酸的量最大。乳酸在发酵过程中被积累并能快速被一些直肠菌群利用而消耗。     

Enzyme activities in cocoa beans during fermentation

The activities of endoprotease, aminopeptidase, carboxypeptidase, invertase (cotyledon and pulp), polyphenol oxidase and glycosidases were studied during heap fermentation of ICS-95 cocoa beans. These enzymes are of key importance in flavour precursor formation and in pigment degradation during cocoa fermentation. Optimal extraction and assay conditions were established to characterise the enzymes reactions and to quantify and compare enzyme activities during cocoa fermentation. The enzymes exhibited large differences in pH optima and stability during fermentation. Aminopeptidase, invertase (cotyledon and pulp) and polyphenol oxidase were strongly inactivated, carboxypeptidase was partly inactivated, whereas endoprotease and glycosidases remained active throughout the fermentation. Since many enzymes are inactivated during fermentation, it is generally recognised that the actual period of enzyme action is short. Although our results confirmed total inactivation for some enzymes, we show that several key enzymes are not completely inactivated during fermentation. Therefore, some enzyme reactions can continue throughout the whole fermentation process. Only polyphenol oxidase was strongly inactivated during sun and artificial drying of the beans. The other enzymes were stable during the drying process. Enzymes like endoprotease and glycosidases are still active in properly fermented and dried beans. © 1998 SCI.     

Effect of fermentation time and drying temperature on volatile compounds in cocoa

The effects of fermentation time and drying temperature on the profile of volatile compounds were evaluated after 2, 4, 6, and 8 fermentation days followed by drying at 60, 70 and 80 °C. These treatments were compared with dry cocoa controls produced in a Samoa drier and by a sun-drying process. A total of 58 volatile compounds were identified by SPME-HS/GC-MS and classified as: esters (20), alcohols (12), acids (11), aldehydes and ketones (8), pyrazines (4) and other compounds (3). Six days of fermentation were enough to produce volatile compounds with flavour notes desirable in cocoa beans, as well as to avoid the production of compounds with off-flavour notes. Drying at 70 and 80 °C after six fermentation days presented a volatile profile similar to the one obtained by sun drying. However, drying at 70 °C represents a lower cost. Given the above results, in the present study the optimal conditions for fermentation and drying of cocoa beans were 6 days of fermentation, followed by drying at 70 °C.     

辣椒素对肠道菌体外发酵的影响

食用辣椒会带来肠道不适反应,对肠道环境存在潜在影响.实验拟通过体外发酵验证辣椒素对肠道发酵环境的影响.向大鼠盲肠内容物发酵液中添加0.05％、0.10％、0.15％三种浓度辣椒素,培养10h后检测发酵液中pH、游离氨、短链脂肪酸(SCFA)及双歧杆菌、乳酸杆菌、大肠杆菌3种微生物的变化趋势,探讨辣椒素对肠道发酵环境的影响.结果表明,与空白组相比,添加辣椒素使盲肠内容物发酵液pH、游离氨浓度升高,短链脂肪酸含量降低,双歧杆菌、乳酸杆菌数量下降,而大肠杆菌数量上升.所有变化均与辣椒素添加剂量存在相关性.研究结果表明,辣椒素对肠道发酵环境有潜在危害.     

生物化学在发酵工程中的基础作用

生物化学是一门迅速发展的现代自然科学,生物化学不断从化学、物理、生物学等有关学科的新成就、新技术中吸收丰富的研究成果,互相渗透而成为独立的学科,生物化学是发酵工业的重要理论基础,由于微生物细胞内酶系统的种类和性质的差别,带来微生物代谢类型的多样性和复杂性,物质代谢的调节及控制对提高产品的质和量提供重要的理论根据,生物化学阐明发酵机理,选择合理工艺途径,提高产品质量,探索发酵新工艺,半个多世纪以来,生物化学已经深入揭示了糖类、脂类、蛋白质、核酸等物质的新陈代谢过程,作为工业发酵的基础支持理论,生物化学进一步在秀彻理解各类生物活性物质的性质基础上,探讨了细胞新陈代谢过程,作为工业发酵的基础支持理论,生物化学进一步在船长过程,并进一步讲述了分子遗传学基础,细胞代谢调控这一部分理论更是工业发酵产品积累的基础（众所周知,根据细胞经济学,细胞不会在体内或体外积累能量物质或代谢次级产物）,工业发酵不断溶合现代生物技术,另一方面,也促进了生物化学的不断进步。     

The microbiology of cocoa fermentation and its role in chocolate quality

The first stage of chocolate production consists of a natural, seven-day microbial fermentation of the pectinaceous pulp surrounding beans of the tree Theobroma cacao. There is a microbial succession of a wide range of yeasts, lactic-acid, and acetic-acid bacteria during which high temperatures of up to 50 degrees C and microbial products, such as ethanol, lactic acid, and acetic acid, kill the beans and cause production of flavor precursors. Over-fermentation leads to a rise in bacilli and filamentous fungi that can cause off-flavors. The physiological roles of the predominant micro-organisms are now reasonably well understood and the crucial importance of a well-ordered microbial succession in cocoa aroma has been established. It has been possible to use a synthetic microbial cocktail inoculum of just 5 species, including members of the 3 principal groups, to mimic the natural fermentation process and yield good quality chocolate. Reduction of the amount of pectin by physical or mechanical means can also lead to an improved fermentation in reduced time and the juice can be used as a high-value byproduct. To improve the quality of the processed beans, more research is needed on pectinase production by yeasts, better depulping, fermenter design, and the use of starter cultures.     

Tobacco use in six economically disadvantaged communities in the Dominican Republic.

The Dominican Republic is a tobacco-growing country, and tobacco control efforts there have been virtually nonexistent. This study provides a first systematic surveillance of tobacco use in six economically disadvantaged Dominican Republic communities (two small urban, two peri-urban, two rural; half were tobacco growing). Approximately 175 households were randomly selected in each community (total N = 1,048), and an adult household member reported on household demographics and resources (e.g., electricity), tobacco use and health conditions of household members, and household policies on tobacco use. Poverty and unemployment were high in all communities, and significant gaps in access to basic resources such as electricity, running water, telephones/cell phones, and secondary education were present. Exposure to tobacco smoke was high, with 38.4% of households reporting at least one tobacco user, and 75.5% allowing smoking in the home. Overall, 22.5% reported using tobacco, with commercial cigarettes (58.0%) or self-rolled cigarettes (20.1%) the most commonly used types. Considerable variability in prevalence and type of use was found across communities. Overall, tobacco use was higher in males, illiterate groups, those aged 45 or older, rural dwellers, and tobacco-growing communities. Based on reported health conditions, tobacco attributable risks, and World Health Organization mortality data, it is estimated that at least 2,254 lives could potentially be saved each year in the Dominican Republic with tobacco cessation. Although it is expected that the reported prevalence of tobacco use and health conditions represent underestimates, these figures provide a starting point for understanding tobacco use and its prevalence in the Dominican Republic.     

发酵蔬菜菌种应用及菌群调控研究进展

蔬菜发酵是控制一定生产条件,通过微生物代谢活动对新鲜蔬菜进行冷加工,以保持蔬菜的营养和提高风味品质的一种方式.发酵蔬菜中的菌群决定了产品的风味特征、营养功能和安全性,同时菌群也影响发酵成品的保藏性能.文章综述了近年来发酵蔬菜微生物多样性和基于多组学技术的微生物作用机理研究进展,分析了发酵蔬菜中功能菌种的选育、应用和影响...     

Molecular identification and pectate lyase production by Bacillus strains involved in cocoa fermentation

We have previously reported the implication of Bacillus in the production of pectinolytic enzymes during cocoa fermentation. The objective of this work was to identify the Bacillus strains isolated from cocoa fermentation and study their ability to produce pectate lyase (PL) in various growth conditions. Ninety-eight strains were analyzed by Amplified Ribosomal DNA Restriction Analysis (ARDRA). Four different banding patterns were obtained leading to the clustering of the bacterial isolates into 4 distinct ARDRA groups. A subset of representative isolates for each group was identified by 16S rRNA gene partial sequencing. Six species were identified: Bacillus subtilis, Bacillus pumilus, Bacillus sphaericus, Bacillus cereus, Bacillus thuringiensis, together with Bacillus fusiformis which was isolated for the first time from cocoa fermentation. The best PL producers, yielding at least 9 U/mg of bacterial dry weight, belonged to B. fusiformis, B. subtilis, and B. pumilus species while those belonging to B. sphaericus, B. cereus and B. thuringiensis generally showed a low level of activity. Two kinds of PL were produced, as revealed by isoelectrofocusing: one with a pI of 9.8 produced by B. subtilis and B. fusiformis, the other with a pI of 10.5 was produced by B. pumilus. Strains yielded about 2 fold more PL in a pectic compound medium than in glucose medium and maximum enzyme production occurred in the late stationary bacterial growth phase. Together all these results indicate that PL production in the bacilli studied is modulated by the growth phase and by the carbon source present in the medium.     

不同产地蓝珀的荧光光谱特征

采用荧光光谱仪对多米尼加、墨西哥、缅甸三个产地蓝珀进行荧光光谱分析,旨在对比不同产地蓝珀的荧光光谱和发光特征.通过实验测试得到了蓝珀样品的光谱曲线及最佳激发光源、测试范围,分析了不同产地蓝珀的峰形、峰位及荧光强度与光谱平滑程度的关系.结果表明:不同产地蓝珀强荧光发射主要发生在可见光的蓝色区域.(1)多米尼加蓝珀的峰形为两个主峰及一个肩峰,分别位于450、474和507 nm附近,其中荧光为蓝色系列的多米尼加蓝珀两个主峰等高,荧光为蓝绿色系列的多米尼加蓝珀样品位于474 nm处主峰强度高于450 nm处;(2)墨西哥蓝珀的最佳激发光源不定,为一个多峰叠加的宽峰,主峰位于439 nm附近.但当样品荧光很强时出现两个分离峰,分别位于415、435 nm;(3)缅甸蓝珀的峰形和峰位与多米尼加蓝珀相似,主峰及肩峰分别位于450、475和508 nm附近,且450 nm主峰强度高于475 nm处,但荧光变弱时,最佳激发光源为399 nm,主峰位于433、451 nm;(4)不同产地蓝珀在相同光源照射条件下所呈现的荧光颜色及强度不同,所表现出的荧光光谱亦有差异.因此,蓝珀的荧光光谱可作为分析其荧光特征的研究手段之一.产生蓝色、蓝绿色荧光的原因,依据前人研究成果及本文的测试数据验证,发现主要是由芳香族化合物产生,初步推测为蒽、二萘嵌苯或其衍生物,不同产地蓝珀的荧光光谱存在差异,可能与引起荧光物质的相对含量及品种不同有关.     

Performance of different fermentation methods and the effect of their duration on the quality of raw cocoa beans

This study aims to compare the effect of three cocoa fermentation methods and their duration on raw cocoa quality. Results showed a decrease in percentage of physical quality defects on fermentation method. Cocoa fermented for 4 days presented higher percentage of purple beans reached 45% and about 10% of slaty beans than cocoa fermented for 6 days whatever the process. Fermentation duration did not influence the mouldy beans that were around 1%. Formation of brown beans increased from 16% to 50% depending on the fermentation duration and process. Using wooden boxes allowed higher percentage of 77%–90% brown beans than others materials. Acidity of cocoa decreased on fermentation duration but beans treated in boxes were significantly (P = 0.05) acidic from 1.40 and 3.07 meq of NaOH g^?1. Fungal population did not vary in number depending both on the duration and the fermentation method with rates that ranged from 3.32 × 10⁷ to 8.63 × 10⁷ CFU g^?1.     

Proteolytic activity (aspartic endoproteinase and carboxypeptidase) of cocoa bean during fermentation

This study was carried out to examine the changes in cocoa aspartic endoproteinase and carboxypeptidase activities, mass pH and temperature during 144 h (6 days) of fermentation using shallow wooden boxes. The results showed that at 72 h of fermentation, the activity of aspartic endoproteinase was higher than the original value. However, at 96 h the carboxypeptidase activity was higher than its original activity. The study also found a high correlation 0·99 (P<0·05) between the mass temperature with the aspartic endoproteinase at 48 h of fermentation. No correlation was found between the mass pH and temperature with the carboxypeptidase during fermentation. The degradation of vicilin-class globulin was about 88·8% and that of albumin was 47·4% at the end of fermentation. © 1998 SCI.     

Influencing cocoa flavour using Pichia kluyveri and Kluyveromyces marxianus in a defined mixed starter culture for cocoa fermentation

The potential impact of aromatic and pectinolytic yeasts on cocoa flavour was investigated using two defined mixed starter cultures encompassing strains of Pichia kluyveri and Kluyveromyces marxianus for inoculating cocoa beans in small scale tray fermentations. Samples for microbial and metabolite analysis were collected at 12–24 hour intervals during 120 h of fermentation. Yeast isolates were grouped by (GTG)₅-based rep-PCR fingerprinting and identified by sequencing of the D1/D2 region of the 26S rRNA gene and the actin gene. Pulsed Field Gel Electrophoresis (PFGE) was conducted on isolates belonging to the species P. kluyveri and K. marxianus to verify strain level identity with the inoculated strains. Furthermore, Denaturing Gradient Gel Electrophoresis (DGGE) was performed to follow yeast and bacterial dynamics over time including the presence of the bacterial inoculum consisting of Lactobacillus fermentum and Acetobacter pasteurianus. Yeast cell counts peaked after 12 h of fermentation with the predominant species being identified as Hanseniaspora opuntiae and Hanseniaspora thailandica. P. kluyveri and K. marxianus were found to compose 9.3% and 13.5% of the yeast population, respectively, after 12 h of fermentation whilst PFGE showed that ~ 88% of all P. kluyveri isolates and 100% of all K. marxianus isolates were identical to the inoculated strains. Despite never being the dominant yeast species at any stage of fermentation, the un-conched chocolates produced from the two inoculated fermentations were judged by sensory analysis to differ in flavour profile compared to the spontaneously fermented control. This could indicate that yeasts have a greater impact on the sensory qualities of cocoa than previously assumed.     

植物乳杆菌对辣白菜发酵过程中风味物质及菌群结构的影响

对比接种发酵和自然发酵辣白菜样品,研究植物乳杆菌的接种对辣白菜风味和微生物结构的影响。检测2种不同处理样品中乳酸菌数量、可滴定酸、还原糖和氨基酸含量以及挥发性风味物质在发酵过程中的变化,通过高通量测序分析菌群结构。接种发酵样品中乳酸菌数量提前2 d达到最大值lg 7. 34 CFU/g,且在发酵第7天时乳杆菌属含量占乳酸菌总数的98. 16%,但物种丰度明显降低;接种发酵组中样品可滴定酸含量在第5天时积累量达到0. 52%;此外,接种发酵组样品中还原糖含量和氨基酸含量均高于自然发酵组;两样品中共检测出84种挥发性风味成分,发酵剂的接种导致样品中二甲基硫化物含量明显增加。植物乳杆菌作为单菌种发酵剂,能加快发酵进程,缩短发酵时间并达到改变菌群结构和改善风味的目的,为辣白菜工业化产品品质控制奠定基础。     

Behavior of Salmonella during fermentation,drying and storage of cocoa beans

Due to cocoa being considered a possible source of Salmonella contamination in chocolate, the behavior of Salmonella during some cocoa pre-processing stages (fermentation, drying and storage) was investigated. The fermentation process was carried out on a pilot scale (2 kg beans/box) for 7 days. Every day a fermentation box was inoculated with a Salmonella pool (ca. 4 log MPN/g). The results showed that Salmonella did not affect (P > 0.05) the growth of the main microorganism groups involved in cocoa fermentation. On the other hand, the pathogen was influenced (P < 0.05) by yeast, acetic acid bacteria and pH. In spite of Salmonella showing counts ≤ 1 log MPN/g in the first days, at the end of fermentation it grew in all samples, reaching counts as high as 7.49 log MPN/g. For drying and storage, cocoa beans were inoculated during the fermentation (experiment A) or during the drying (experiment B). In these stages the decline of the water activity affected the pathogen behavior. In experiment A during the drying, Salmonella count increased in most of the samples. In experiment B either a slight growth or no growth in the samples inoculated up to 48 h was observed, whereas the other samples showed reductions from the initial count. After 30 days of storage at room temperature, the water activity decreased to 0.68, and reductions of Salmonella ranged from 0.93 to 2.52 log MPN/g. Despite the reductions observed during the storage, the pathogen was detected even after 120 days. Therefore, the results showed that Salmonella growth or survival depends on when the contamination occurs.     

DNA指纹图谱技术在奶酪发酵菌群中的应用研究

DNA指纹图谱技术是近年来较为常用的分子生物学技术,由于发酵菌群的DNA指纹图谱直接反映DNA水平上的差异,因而作为微生物指纹图谱的一个组成部分,DNA指纹图谱这一现代分子生物学技术在微生物研究中有其独特的作用,这种技术在发酵菌群的鉴定、遗传育种及多样性等研究领域有广阔的应用前景。常用于发酵菌群研究的DNA指纹图谱技术有RFLP、T-RFLP、SSCP、RAPD、DGGE、AFLP等。本论文在综合介绍DNA指纹图谱的一般常用技术的基础上,结合近年来国内外奶酪发酵菌群中DNA指纹图谱技术研究现状,在探讨其在奶酪发酵菌群相关领域应用的基础上,逐一介绍了各种技术的原理、优缺点及研究现状,对我国传统奶酪发酵菌群的研究具有重要的实际意义与理论价值。     

Effect of the solid state fermentation of cocoa shell on the secondary metabolites,antioxidant activity,and fatty acids

During cocoa (Theobroma cacao L.) processing, the accumulated cocoa shell can be used for bioconversion to obtain valuable compounds. Here, we evaluate the effect of solid-state fermentation of cacao flour with Penicillium roqueforti on secondary metabolite composition, phenol, carotenoid, anthocyanin, flavonol, and fatty acids contents, and antioxidant activity. We found that the total concentrations of anthocyanins and flavonols did not change significantly after fermentation and the phenolic compound and total carotenoid concentrations were higher. The fermentation process produced an increase in saponin concentration and antioxidant activity, as well as significant changes in the levels of oleic, linoleic, gamma-linolenic, and saturated fatty acids. Based on our findings, we propose that the reuse of food residues through solid state fermentation is viable and useful.     

Microbial development during tempeh fermentation from various beans and effect of Lactobacillus plantarum on the natural microflora

The microbial development during the fermentation of tempeh made of unacidified and acidified horsebean, pea, chickpea and soybean was studied. Increase in microbial count was observed during the fermentation of the various beans. Bacillus spp. and coryneform bacteria dominated the microflora of unacidified, and streptococci of acidified horsebean tempeh. In pea tempeh, lactobacilli dominated, in chickpea, micrococci, staphylococci and coryneform bacteria and in soybean tempeh, enterococci were the dominant genera. Inoculation of the cooked beans with Lactobacillus plantarum resulted in a lower pH and lower total counts in the various products. The use of Lb. plantarum in tempeh production may control the proliferation of undesirable microorganisms.     

糜米发酵液的研究

采用正交实验探讨了烫米温度、豆面加入量、加水量、培养温度、pH变化对糜米发酵液的影响。确定了在80℃烫米,加入2%豆面,米水比为1∶1.6时,有氧变温培养24h,得到pH=3.5,风味较好的糜米发酵液,并对发酵液中的氨基酸和粗多糖进行测定。