Characteristics of scalded dough fermented by co-cultures of Saccharomyces cerevisiae Y10, Wickerhamomyces anomalus Y13 and Torulaspora delbrueckii Y22

Scalding process could change properties of dough. Co-culture of yeasts could improve the quality of product. In this study, characteristics of scalded dough with co-cultures of Saccharomyces cerevisiae Y10, Wickerhamomyces anomalus Y13 and Torulaspora delbrueckii Y22 were investigated. Most starch granules lost shape and crystal pattern after scalding, meanwhile, gluten network had become weak, suggesting the gelatinisation of starch and damage of gluten protein. After fermentation, Y13 and Y22 cell populations increased rapidly. However, the cell number of Y10 decreased from 6.91 Lg CFU per gram dough to 5.42 Lg CFU per gram dough. Gluten protein aggregated into chunks after 8 h of fermentation, meanwhile, the water molecules in dough were bound more tightly. These results indicated that scalded dough provide a unique environment for the growth of yeasts, and further affect the characteristics of dough during fermentation.     

Interdependence of Escherichia coli formate dehydrogenase and hydrogen-producing hydrogenases during mixed carbon sources fermentation at different pHs

The impact of the four membrane-bound [NiFe]-hydrogenases (Hyd) of Escherichia coli on total H₂-oxidizing activity during fermentation of a mixture of glucose, glycerol and formate at different pHs was examined. It was shown that Hyd-2 had a major contribution to total Hyd activity at pH 7.5 in early-stationary phase (24 h) cells, while the main contribution was made by Hyd-3 in late-stationary phase (72 h). Hyd-4-dependent Hyd activity could be demonstrated at pH 6.5 in cells lacking Hyd-1, Hyd-2 and Hyd-3. at pH 7.5 Hyd-4-dependent formate dehydrogenase (FDH-H) activity was demonstrated. Growth properties and fermentation end product patterns during 72 h demonstrated that the cells retained viability deep into stationary phase. Our findings emphasize the importance of formate in modulating H₂ metabolism, presumably by contributing to maintain redox, pH and pmf balance. This is important for regulating and enhancing H₂ production when a mixture of carbon sources is applied.     

Preparation of grape seed polypeptide and its calcium chelate with determination of calcium bioaccessibility and structural characterisation

Grape seed polypeptide (GSPP) was obtained by liquid fermentation with Bacillus subtilis TK15.015 from waste grape seed pomace. Its chelation ability with calcium ions was excellent. Simulation of in vitro gastrointestinal digestion showed that GSPP and calcium chelate (GSPP-Ca) slowly released calcium and decreased stomach stimulation. The solubility and transmission rate of GSPP-Ca after digestion in the gastrointestinal tract for 8 h maintained high levels of 74.4% and 46.4%, respectively, which far exceeded the levels achieved by other calcium supplements. Structural characterisation showed that calcium ions mainly react with binding sites present in peptides such as carboxyl oxygen, hydroxyl oxygen, amino nitrogen and amide bonds. GSPP-Ca may be a state in which a calcium-encapsulating complex formed, leaving calcium ions in a soluble state, suggesting its possible use as a high-quality calcium supplement.     

5 种乳酸菌对库车小白杏发酵液理化性质及感官评价的影响

用戊糖片球菌、罗伊氏乳杆菌、鼠李糖乳杆菌、植物乳杆菌、嗜酸乳杆菌共5?种乳酸菌发酵库车小白杏，通过比较发酵液在发酵过程中的菌浓度、pH值、总可溶性固形物（total soluble solids，TSS）含量、超氧化物歧化酶（superoxide dismutase，SOD）活性等理化特性及发酵结束后的感官评价，筛选出一种或几种适合发酵库车小白杏发酵液的菌株。结果表明，发酵结束后，戊糖片球菌发酵库车小白杏发酵液的SOD活性达到252.63?U/g，活菌数达到8.07（lg（CFU/mL）），TSS含量降至17.1?°Brix，感官总体评价值最佳达到97%。植物乳杆菌发酵的库车小白杏发酵液的SOD活性达到275.87?U/g，感官总体评价几何平均（geometrical mean，GM）值达到88%。嗜酸乳杆菌发酵的库车小白杏发酵液速度最快，活菌数最终达到9.95（lg（CFU/mL）），TSS含量降至16.6?°Brix，但感官总体评价GM值仅为79%。综上所述，戊糖片球菌是最适合发酵库车小白杏的菌种，而植物乳杆菌和嗜酸乳杆菌的适合度仅次于戊糖片球菌。通过比较5?种乳酸菌发酵的库车小白杏发酵液的理化性质和感官评价，可以得出结论，戊糖片球菌最适合发酵库车小白杏。     

Bacterial community succession and biogenic amine changes during fermentation of fish-chili paste inoculated with different commercial starter cultures

The microbial dynamics, diversity and succession characterisation during the fermentation of fish-chili paste, with and without starter cultures by high-throughput sequencing, were investigated to identify the relationship between microbial composition and the accumulation of biogenic amines. Results showed that Firmicutes was the predominant phylum, and Lactobacillus and Weissella were the main genera during fermentation process, regardless of the inclusion of starter cultures. Compared with naturally fermented samples (NS; no starter cultures), Pediococcus and Staphylococcus flourished in samples inoculated with SBM-52 starter culture (Staphylococcus xylosus + Staphylococcus carnosus + Pediococcus pentosaceus + Pediococcus acidilactici). Staphylococcus also accounted for a larger proportion in samples inoculated with WBX-43 starter culture (Staphylococcus xylosus + Staphylococcus carnosus). Furthermore, Enterobacter was inhibited in inoculated samples. Unweighted pair-group method with arithmetic means and principal component analyses revealed that microbiota structures were different among NS, SBM and WBX samples. In case of biogenic amines, the concentration of putrescine, cadaverine and tyramine increased to higher levels in NS samples compared with inoculated samples. Our work also investigated the relationship between core bacterial communities and biogenic amines. This study provided an improved understanding for the effects of starter cultures on the microbial community and the quality of fish-chili paste.     

油莎豆白酒发酵工艺优化及其品质指标检测

以油莎豆饼和高粱为原料，分别采用固态和液态发酵工艺酿造油莎豆白酒，对油莎豆白酒的发酵工艺进行选择。在此基础上，采用单因素试验及正交试验探究发酵温度、糖化酶添加量以及活性干酵母添加量对油莎豆白酒发酵及理化指标的影响，从而确定油莎豆白酒的最佳固态发酵工艺条件，并对油莎豆白酒发酵过程中酒醅的发酵指标进行实时监测。结果表明，油莎豆白酒的最佳发酵工艺为固态发酵，最佳发酵工艺条件为发酵温度23 ℃，糖化酶添加量190 U/g、活性干酵母添加量0.5‰。在此优化条件下，油莎豆白酒的酒精度为9.2%vol，总酯含量为2.96 g/L，总酸含量为1.45 g/L，乙酸乙酯含量为2.42 g/L，出酒率达到41%。油莎豆白酒发酵过程中，酒精含量逐渐升高，最后趋于平缓，发酵结束后，酒精度达9.2%vol；发酵温度先上升后下降，第6天时酒醅温度达到峰值（27.9 ℃）；剩余淀粉含量逐渐下降，发酵结束后，淀粉消耗12.21%。     

Prebiotic properties of xylooligosaccharide extracted from sugarcane wastes (pith and rind): a comparative study

Wastes from agricultural industry are often disposed. Nevertheless, these wastes contain nutraceuticals and functional compounds. Xylooligosaccharide (XOS) was extracted from two sugarcane wastes (SW); rind (SR) and pith (SP), and the prebiotic properties of both XOS were examined. SR and SP had different mixture of XOS and were resistant towards α-amylase and gastric juice digestion in vitro. Although the growth of Lactobacillus casei Shirota (LcS) and Bifidobacterium animalis subsp. Lactis ATCC® 700541™ increased significantly in both XOS after 48 h of incubation, XOS from SR showed better enrichment of probiotics growth. Both XOS were found to be more fermentable by LcS and acetic acid was the predominant end product of the fermentation. Since XOS composition was different between SR and SP and such difference can affect their prebiotic properties, it is important to choose the appropriate parts of SW to extract XOS with high fermentable properties and obtain the best synbiotics combination.     

Effect of Cultivation Parameters on Fermentation and Hydrogen Production in the Phylum Thermotogae

The phylum Thermotogae is composed of a single class (Thermotogae), 4 orders (Thermotogales, Kosmotogales, Petrotogales, Mesoaciditogales), 5 families (Thermatogaceae, Fervidobacteriaceae, Kosmotogaceae, Petrotogaceae, Mesoaciditogaceae), and 13 genera. They have been isolated from extremely hot environments whose characteristics are reflected in the metabolic and phenotypic properties of the Thermotogae species. The metabolic versatility of Thermotogae members leads to a pool of high value-added products with application potentials in many industry fields. The low risk of contamination associated with their extreme culture conditions has made most species of the phylum attractive candidates in biotechnological processes. Almost all members of the phylum, especially those in the order Thermotogales, can produce bio-hydrogen from a variety of simple and complex sugars with yields close to the theoretical Thauer limit of 4 mol H₂/mol consumed glucose. Acetate, lactate, and L-alanine are the major organic end products. Thermotagae fermentation processes are influenced by various factors, such as hydrogen partial pressure, agitation, gas sparging, culture/headspace ratio, inoculum, pH, temperature, nitrogen sources, sulfur sources, inorganic compounds, metal ions, etc. Optimization of these parameters will help to fully unleash the biotechnological potentials of Thermotogae and promote their applications in industry. This article gives an overview of how these operational parameters could impact Thermotogae fermentation in terms of sugar consumption, hydrogen yields, and organic acids production.     

Anthocyanin-rich fruit vinegar from Grewia and Cantaloupe fruit blends

Grewia is a tropical berry rich in anthocyanins and antioxidants but highly perishable in nature. In this study, desirable composite blend of overripe Grewia (Phalsa) berries and cantaloupe was sought for conversion to acetic acid. Composition of raw macerate, and the alcoholic and acetic ferments was analysed for sugars, alcohol and acetic acid. The primary alcohol yield varied significantly (5.75–99.44%) with blend composition. Vinegar from select blend attained 4.98% acidity with 138.57 mg mL⁻¹ of phenols and high anthocyanins retention (74.77%). Gompertz model was used to fit the growth curves of S. cerevisiae and A. aceti (R²> 0.92) during fermentation. Presence of ethyl acetate, iso-pentyl alcohols explained pleasant sweet fruity aroma of resulting vinegar. Thus, high quality functional red fruit vinegar can be obtained to prevent spoilage and utilise the functional potential of this delicate and nutritious berry.