Solid-substrate fermentation of soybeans with Rhizopus spp.: comparison of discontinuous rotation with stationary bed fermentation

Tempe is a soybean food obtained by stationary solid-substrate fermentation using moulds (mainly Rhizopus spp.) as starter organism. Traditionally, tempe is fermented in static layer trays or wrapped packages. Due to heat and mass transfer limitations, gradients of temperature and gas atmosphere will result. Agitated fermentation can help to level heat and mass gradients, yielding better homogeneity. This type of process will not result in traditional tempe, but in individually fermented soybeans that could be processed into food ingredients. This report deals with the comparative effect of stationary versus agitated solid-substrate fermentation of soybeans on some chemical indices of substrate modification. For agitated solid-substrate fermentation, a 450-l size rotary-drum bioreactor was designed and constructed. Of two Rhizopus spp. tested, R. microsporus tolerated agitation quite well, as judged by changes of pH, amino nitrogen, ammonia, and soluble dry matter. The other species, R. oligosporus was strongly affected by agitation. This resulted in less pH increase (difference approx. 1.5 units), lower amino nitrogen levels (30-50% of levels in static fermentation), and lower levels of water-soluble non-lipid dry matter (30-50% of levels in static fermentation) with R. oligosporus agitated fermentation of soybeans controlled at 30 and 37 degrees C, compared to static fermentation at temperatures ranging between 25-35 and 30-40 degrees C, respectively.     

Structural and Functional Properties of Fermented Soybean (Tempeh) by Using Rhizopus oligosporus

The effect of R. oligosporus on structural and functional properties of fermented soybean was studied. After 24 hours of fermentation, the amount of total free amino acids formed greatly increased in soybean (1.20 g/100 g soybean). The pH of the fermented soybean was neutral during the growth of the mold. The amount of g-amino butyric acid (GABA) gradually increased during fermentation of the soybean (21.4 mg/100 g soybean per 24 hours). The proteins (albumin, globulin, alkaline soluble) were rapidly degraded to amino acids and low-molecular-weight peptides. Instrumental texture of fermented soybean (48 hours) had higher weakness (7.14 N), modulus of elasticity (1.02 × 10⁹ Pa) and surrender value (8.17 × 10⁶ Pa); these values were significantly different (P < 0.05) compared with 24 and 72 hours fermentation. Cell structure of fermented soybean was proportionally disorganized during the course of fermentation. The cell walls, cytoplasm, and vacuoles could not be distinctly identified. R. oligosporus produced enzymes which hydrolyzed protein, lipid, and starch, providing growth substrates and playing a role in its metabolism. Metabolism of mold was attributed to soybean cell disorganization, and the ratio of mature mold became higher, which was indicated by dark color.     

Production of volatile compounds by Rhizopus oligosporus during soybean and barley tempeh fermentation

Rhizopus oligosporus Saito can ferment soybeans or cereal grains to tempeh, a sliceable cake with improved nutritional properties. Volatiles produced by different R. oligosporus strains grown on malt extract agar (MEA), barley and soybean were investigated. The effect of co-cultivation with Lactobacillus plantarum on the production of volatiles was also studied. Volatile compounds were collected in situ by headspace diffusion and identified by GC-MS. The ten R. oligosporus strains that had different colony morphologies on MEA produced very similar volatile profiles, except for slight variations among the minor volatile compounds (e.g. sesquiterpenes). Likewise, practically no differences in volatile profiles were observed between three of the strains grown on soybeans. In contrast, the R. oligosporus volatile profile on soybean was different from that on barley from the same strain. Co-cultivation with L. plantarum did not influence volatile production by R. oligosporus. The dominant compounds produced on all three substrates were ethanol, acetone, ethyl acetate, 2-butanone, 2-methyl-1-propanol, 3-methyl-1-butanol and 2-methyl-1-butanol. Acetaldehyde and 2-methyl-propanal were also produced on MEA and barley, while 2-pentanone, methyl acetate, 2-butanol and 3-methyl-3-buten-1-ol were observed on soybeans. Ethanol, 2-methyl-1-butanol and 3-methyl-1-butanol were the most abundant volatile compounds produced on MEA and barley, while 2-butanone was the dominant volatile metabolite on soybean. The mushroom odour compounds, 3-octanone and 1-octen-3-ol, were only detected from soybean and soybean tempeh.     

根霉发酵豆腐乳蛋白酶活性动态变化研究

通过对豆腐乳发酵过程中游离氨基酸和可溶性蛋白质变化情况的检测,来确定在豆腐乳发酵过程中蛋白酶活性变化情况。结果表明,可溶性多肽的产生呈下降趋势,而游离氨基酸的产生呈上升趋势,前者在20h时出现最大值,后者在24h时出现最大值。     

日本根霉发酵乌龙茶过程中茶叶品质的变化

研究了日本根霉对乌龙茶发酵过程中的品质变化,结果表明,在低温发酵(第一阶段)期间微生物生长旺盛,茶叶的品质有显著的变化,茶多酚和儿茶素的含量呈一定程度的减少,而可溶性糖和茶褐素的含量呈逐渐增加的趋势.在高温(第二阶段)阶段,酶活增大,茶多酚和儿茶素的含量继续减少,可溶性糖和茶褐素的含量都继续增加.其中以低温发酵21d的样品的变化尤为显著,其茶多酚和儿茶素的含量分别下降了54.4%和93.8%,荼汤红褐、醇甘且含有特殊的焦糖香.     

Inhibition of proteases during fermentation improves xylanase production by alkali tolerant Aspergillus fumigatus ARl

An alkali-tolerant Aspergillus fumigatus ARl produced a high level of xylanase (228 U/ml) at 42 h of submerged fermentation at pH 9.0. During later culture periods, xylanase activity declined considerably and reached 45 U/ml at 90 h. This trend is because of proteolytic degradation of xylanases since A. fumigatus co-produced multiple proteases with high activity (120-159 U/ml) during submerged fermentation. Xylanase and protease were found to be active over a wide range of pH from 5.5 to 9.0. In contrast, protease lost its activity completely in the presence of CuSO4 (25 mM) while xylanase remained active. The selective inhibition of proteases by the addition of CuSO4 to the culture medium prevented proteolytic degradation of xylanase and improved the production of xylanase by 3-fold.     

Biological activities of fermented soybean paste (Doenjang) prepared using germinated soybeans and germinated black soybeans during fermentation

To produce doenjang with enhanced biological activities, doenjang was prepared by fermenting regular soybeans (RS), germinated soybeans (GS), and germinated black soybeans (GBS) for 90 days. The isoflavone contents in GS and GBS-doenjang were slightly higher than in RS-doenjang in the early stage of fermentation. The DPPH radical scavenging activity of GBS-doenjang was highest at 70.00% after 30 days of fermentation. The angiotensin-converting enzyme (ACE) inhibiting effects increased as the fermentation period progressed, and were significantly (p<0.05) higher in GBS-doenjang (58.69%) than in other preparations after 75 days of fermentation. The greatest fibrinolytic activities were 127.59 and 100.00% in nontreated GBS-doenjang and GBS-doenjang treated for 30 min at 55°C, respectively. There were significant (p<0.05) correlations between the total isoflavone content and the antioxidant activity (0.779) and between the isoflavone content and the ACE activity-inhibiting effects (0.669). GBS-doenjang exhibited greater antioxidant activities, ACE-inhibition, and fibrinolytic activities than RS and GS-doenjang.     

Growth of lactic acid bacteria and Rhizopus oligosporus during barley tempeh fermentation

The zygomycete Rhizopus oligosporus is traditionally used to ferment soybean tempeh, but it is also possible to ferment other legumes and cereals to tempeh. The traditional soybean tempeh harbours a multitude of microorganisms with potentially beneficial or detrimental effects on quality. Lactic acid bacteria (LAB) have positive effects on the safety of soybean tempeh, but the effects of LAB on R. oligosporus growth have not been investigated. We have developed a cereal grain tempeh by fermenting pearled barley with R. oligosporus ATCC 64063. Four LAB species, Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus reuteri and Lactococcus lactis were assessed for their growth abilities and their effects on R. oligosporus growth during barley tempeh fermentation. Growth of LAB was assayed as colony forming units (cfu), while growth of R. oligosporus was measured as ergosterol content and hyphal length. The two fungal measurements highly correlated (r=0.83, P<0.001, n=90). The ergosterol content of fungal mycelia ranged from 11.7 to 30.1 mg/g fungal dry matter. L. plantarum multiplied from 4.8 to 7.4 log cfu/g dry tempeh and L. fermentum increased from 4.4 to 6.8 log cfu/g during 24 h incubation at 35 degrees C. L. reuteri and L. lactis had significantly slower growth, with increases from 4.8 to 5.6 log cfu/g and 5.0 to 5.4 log cfu/g, respectively. The growth of R. oligosporus and the final pH (4.9) in barley tempeh were not significantly influenced by any of the LAB investigated.     

Zearalenone production by Fusarium species isolated from soybeans

The incidence of species of Fusarium in soybeans and their ability to produce zearalenone was evaluated. Fusarium species were present in 5% of the beans examined. Of 43 isolates 41.8% were toxinogenic, belonging to the following species (number of zearalenone producers/number of isolates tested): F. equiseti (5/11), F. semitectum (13/24), F. moniliforme (0/6) and Fusarium spp. (0/2). Two high zearalenone producing isolates of F. equiseti and F. semitectum produced on rice 2.050 and 1.370 μg of zearalenone per g of substrate, respectively. When these strains were inoculated on soybeans detectable amounts of zearalenone were not produced although the fungi grew vigorously. This suggests that soybeans are not a good substrate for the biosynthesis of zearalenone by Fusarium species.     

黑根霉固态发酵产木聚糖酶的研究

利用黑根霉降解甘蔗渣固态发酵生产木聚糖酶,运用正交试验研究了甘蔗渣与麸皮的比例、氮源、pH值、培养时间、水料比等对产木聚糖酶活力的影响。结果表明:甘蔗渣:麸皮为6:4,氮源为酵母膏,pH值为5,培养时间为5d,水料比为2.5:1,产酶量达406.18U/g。     

根霉产纤溶酶液体发酵培养基的优化

通过单因素,均匀设计和正交试验,从碳氮比、无机氮源、胰蛋白胨、pH值方面优化了根霉液体发酵产生纤溶酶的培养基组成.试验结果表明,试验范围内菌株液体发酵产纤溶酶的适宜培养基组成为:麸皮水5.6%,豆粕水解液5.3%,二者体积比为2∶3,磷酸氢二铵0.4%,硝酸钠0.5%,pH值自然.优化培养基的纤溶酶酶活力为140.00U/mL.     

匍枝根霉纤维素酶发酵条件优化及分批发酵动力学模型的构建

以滤纸酶活为检测指标,通过单因素实验和均实验设计优化匍枝根霉产纤维素酶培养条件,并以此为基础进行分批发酵,并利用Logistic方程和Luedeking-Piret方程构建动力学模型。优化结果表明:滤纸酶活在发酵时间为84 h时达到13.16 IU/mL,比优化前提高了149%,其中,内切酶活、外切酶活和β-葡萄糖苷酶活高值分别为45.81 IU/mL、0.537 IU/mL和12.45 IU/mL且所建模型拟合良好。     

Monascus-mediated fermentation improves the nutricosmetic potentials of soybeans

Food Science and Biotechnology - The potential nutricosmetic activities and compositional changes of 80% ethanol extracts of white soybean (MFWS) and black soybean (MFBS) fermented with Monascus...     

米根霉发酵木薯淀粉产L-乳酸的工艺优化

以培养基配方（糖化液、蛋白胨、酵母膏、麦芽粉添加量）和培养条件（培养温度、pH、培养时间、接种量）的单因素试验结果为 依据,选取糖化液质量分数、培养时间、pH和培养温度4因素,以发酵液中L-乳酸含量为评价指标,基于Box-Behnken试验设计响应面 法优化了米根霉发酵木薯淀粉产L-乳酸的发酵工艺参数。 结果表明,最优发酵工艺参数为糖化液26%、蛋白胨6 g/L、酵母浸膏4 g/L、 麦芽粉10 g/L、KH2PO4 0.3 g/L、MgSO·4 7H2O 0.4 g/L、ZnSO4·7H2O 0.3 g/L、CaCO3 45 g/L、培养时间80 h、培养温度29 ℃、初始pH 5.5、接 种量6%。 该优化条件下,发酵液中L-乳酸的含量可达84.33 g/L,发酵液中葡萄糖对L-乳酸的转化率为71.34%,其光学纯度为75.62%, 比旋光度为+2.12。     

Plackett-Burman和Box-Benhnken Design实验设计法优化华根霉产糖化酶发酵培养基的研究

应用Plackett-Burman设计法对影响华根霉发酵的培养基组分进行筛选,所选取的11个相关因素为:葡萄糖、麦芽糖、蔗糖、橄榄油、蛋白胨、黄豆粉、酪蛋白胨、麦麸、MgSO4·7H2O、K2HPO4、KH2PO4。确定影响产糖化酶活的关键因素为橄榄油、酪蛋白胨、麦麸,接着进行最陡爬坡实验逼近3个关键因素的最大响应区域。在此基础上,采用Box-BenhnkenDesign实验设计法对发酵培养基组分进行优化,得出最佳条件。此时橄榄油为0.01%、酪蛋白胨为8.14%、麦麸为4.32%、糖化酶活为18.7U,比优化前提高81%。     

匍枝根霉淀粉发酵产纤维素酶的条件研究

以匍枝根霉TP-02(Rhizopus stolonifer TP-02)为出发菌株,首次利用淀粉水解液为主要碳源,快速合成纤维素酶。从碳源、氮源、培养温度、初始p H、装液量和接种量等方面研究该菌株的产酶条件。获得最佳培养基和培养条件为:10%淀粉水解液,麸皮浸出汁5%,NH_4Cl 0.5%,KH_2PO_40.5%,MgSO_4·7H_2O 0.4%,CaCl_20.4%,酵母粉0.6%;发酵温度30℃,装液量80 m L/(250 m L),初始p H 5.0,接种量8%。通过摇瓶实验优化培养基和培养条件后,获得滤纸酶活为9.66 IU/m L。研究中进一步利用该培养基在5 L发酵罐中发酵至60 h时酶活达到最大值,其中滤纸酶活、外切酶活、内切酶活和β-葡萄糖苷酶分别为16.51、15.39、11.48和6.17 IU/m L。与以往纤维素类物质为碳源发酵产纤维素酶相比,淀粉水解液发酵获得的纤维素酶酶系组成有了较大的变化,特别是关键的外切酶活有了大幅度提高,而发酵时间缩短了将近1倍。     

优化密码子及诱导温度提高雪白根霉脂肪酶在毕赤酵母中的表达

根据毕赤酵母密码子的偏好性,通过在线软件对雪白根霉脂肪酶基因(rnl)进行密码子优化。优化后的脂肪酶基因(rnl-opt)GC含量由原来的46%提高到49%,碱基A,T,C,G均匀分布,减少了AT和GC富集区,适应指数由0.82提升到0.85。将rnl-opt连接到表达载体p PICZαA并转入毕赤酵母X33中。将含有rnl和rnlopt的重组工程菌在摇瓶和50 L发酵罐中进行诱导表达。摇瓶培养条件下,含有rnl和rnl-opt重组工程菌的最大酶活分别为458、956 U/m L。50 L发酵罐培养条件下,含有rnl和rnl-opt重组工程菌的最大酶活和总蛋白浓度分别为14 856、30 500 U/m L和3.61、7.8 g/L。为了进一步提高含rnl-opt重组工程菌的表达酶活,对其在50L发酵罐培养的诱导温度进行优化,当诱导温度为22℃时,含rnl-opt重组工程菌的酶活和细胞湿重均达到最大值分别为39 520 U/m L和461 g/L。相对于30℃,酶活和细胞湿重分别提高了30%和16%。     

Proteolysis characteristics of Actinomucor elegans and Rhizopus oligosporus extracellular proteases under acidic conditions

Enzymatic hydrolysis of soybean protein isolate by the extracellular proteases from Actinomucor elegans and Rhizopus oligosporus at pH 3.0, 3.5, 5.0, 5.5 and 6.0 was investigated. The activity of the A. elegans protease is lower than that of R. oligosporus, but both proteases exhibit considerable degradation of soybean protein at pH 5.5 and 6.0. The water‐soluble protein content and the degree of hydrolysis of the hydrolysates are increased significantly, and bitterness values are very low. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE) reveals that these proteases have different cutting sites on peptide polymers. At pH 5.5, there is a lower content of total free amino acids (39.20 mg per 100 mL; 62.68% hydrophobic amino acids) in the R. oligosporus protease hydrolysate. In conclusion, treatment with R. oligosporus protease at pH 5.5 achieves efficient degradation of soybean protein, suggesting a promising industrial process for making bitterless protein hydrolysates.     

霞多丽葡萄自然发酵过程中酵母种群的分布与变化规律

采用WL形态学归类分析和5.8S-ITS rDNA PCR-RFLP分子生物学鉴定方法,对我国2个主要产区所产白葡萄品种霞多丽自然发酵过程中的酵母种群进行了系统研究。结果表明,从霞多丽葡萄发酵液中分离到7个酵母菌种,不同产区霞多丽发酵液中分布酵母菌的种类和数量有一定差别,但在发酵过程中酵母种群的变化趋势是一致的。