铁皮石斛发酵酒品质特性研究

以铁皮石斛为原料，研究了产乳酸芽孢杆菌（Bacillus sp.）DU-106和酿酒酵母菌（Saccharomyces cerevisiae）171发酵铁皮石斛酒的理化性质，并测定了发酵前后的活性成分、有机酸组成及含量、发酵酒体组成成分变化。结果表明，最佳发酵条件为芽孢杆菌∶酿酒酵母=1∶10（V/V），接种2%菌种活化液，30 ℃发酵7 d。此优化条件下，铁皮石斛酒的pH值为3.75，总酸含量为0.98%，酒精度为5.2%vol，可溶性固形物含量8%。发酵后多糖含量增加至4.99 g/L，花色苷含量增加至16.82 mg/L，有机酸含量发生明显变化，其中酒石酸、乳酸、乙酸、柠檬酸含量分别升高至280.39 mg/L、126.28 mg/L、55.19 mg/L、16.78 mg/L，苹果酸含量由53.01 mg/L降低至33.86 mg/L，且发酵前后组分差异显著，发酵后产生了2,5-二羟基-3-噻吩羧酸等化合物。混合菌发酵促进了铁皮石斛中有益物质的溶出，提高了铁皮石斛酒的营养价值。     

不同酿酒酵母对山葡萄北国蓝蒸馏酒挥发性物质的影响

以市场上常见的8种活性干酵母作为山葡萄北国蓝的发酵剂，通过比较发酵速率、定性定量分析蒸馏酒中香气成分，并结合主成分分析（PCA），综合得出适合酿造山葡萄北国蓝蒸馏酒的酿酒酵母。结果表明，在发酵过程中，发酵速率最快的是酵母ADT，酵母CEC01次之；发酵完成后，酵母菌MST的发酵原酒酒精度最高，为（9.80±0.11）%vol，发酵最彻底，产酒能力优于其他酵母（P＜0.05），其次是酵母CEC01，为（9.79±0.01）%vol；酵母菌CEC01发酵的山葡萄蒸馏酒中挥发性物质含量最高，为16 394.24 μg/L，其次是酵母VF（16 163.22 μg/L）、ADT（15 576.32 μg/L）；主成分分析综合得分最高的是酵母CEC01，其次是酵母ADT。由此可得，酵母CEC01、ADT发酵能力强，产酒率高，且蒸馏酒的酒香浓郁、品质较好，适合酿造山葡萄蒸馏酒。     

Dhh1 is a member of the SESA network

The correct separation of chromosomes during mitosis is necessary to prevent genetic instability and aneuploidy, which are responsible for cancer and other diseases, and it depends on proper centrosome duplication. In a recent study, we found that Smy2 can suppress the essential role of Mps2 in the insertion of yeast centrosome into the nuclear membrane by interacting with Eap1, Scp160, and Asc1 and designated this network as SESA (S my2, E ap1, S cp160, A sc1). Detailed analysis showed that the SESA network is part of a mechanism which regulates translation of POM34 mRNA. Thus, SESA is a system that suppresses spindle pole body duplication defects by repressing the translation of POM34 mRNA. In this study, we performed a genome-wide screening in order to identify new members of the SESA network and confirmed Dhh1 as a putative member. Dhh1 is a cytoplasmic DEAD-box helicase known to regulate translation. Therefore, we hypothesized that Dhh1 is responsible for the highly selective inhibition of POM34 mRNA by SESA.     

The effect of moderate pulsed electric fields on autolysis of Saccharomyces cerevisiae and the amino acid content in autolysates

The effect of moderate pulsed electric fields (MPEF) strength on autolysis of Saccharomyces cerevisiae was evaluated in this study. After exposure to MPEF with intensity of 7 kV cm⁻¹ for 4 ms, the integrity of the cell wall was obviously destroyed and the inactivation of S. cerevisiae reached 99.43%. During the subsequent 42-h autolysis process, the release of free α-amino nitrogen of MPEF-treated cells, as well as extracellular protease activity, was significantly (P < 0.05) higher than that of untreated cells. Moreover, exposure to 7 kV cm⁻¹ led to an increase of the total amino acid of 149.36%. In particular, the content of aspartic acid and glutamic acid which are important umami flavour precursors increased by 232.55% and 209.40%, respectively. These results indicate that MPEF will be an effective method to accelerate autolysis of S. cerevisiae for obtaining high-quality yeast extract as flavour enhancers and nutrition supplements.     

Quantifying the efficiency and biases of forest Saccharomyces sampling strategies

Saccharomyces yeasts are emerging as model organisms for ecology and evolution, and researchers need environmental Saccharomyces isolates to test ecological and evolutionary hypotheses. However, methods for isolating Saccharomyces from nature have not been standardized, and isolation methods may influence the genotypes and phenotypes of studied strains. We compared the effectiveness and potential biases of an established enrichment culturing method against a newly developed direct plating method for isolating forest floor Saccharomyces spp. In a European forest, enrichment culturing was both less successful at isolating Saccharomyces paradoxus per sample collected and less labour intensive per isolated S. paradoxus colony than direct isolation. The two methods sampled similar S. paradoxus diversity: The number of unique genotypes sampled (i.e., genotypic diversity) per S. paradoxus isolate and average growth rates of S. paradoxus isolates did not differ between the two methods, and growth rate variances (i.e., phenotypic diversity) only differed in one of three tested environments. However, enrichment culturing did detect rare Saccharomyces cerevisiae in the forest habitat and also found two S. paradoxus isolates with outlier phenotypes. Our results validate the historically common method of using enrichment culturing to isolate representative collections of environmental Saccharomyces. We recommend that researchers choose a Saccharomyces sampling method based on resources available for sampling and isolate screening. Researchers interested in discovering new Saccharomyces phenotypes or rare Saccharomyces species from natural environments may also have more success using enrichment culturing. We include step-by-step sampling protocols in the supplemental materials.     

Saccharomyces cerevisiae and Hanseniaspora uvarum mixed starter cultures: Influence of microbial/physical interactions on wine characteristics

The growing trend in the wine industry is the revaluation of the role of non-Saccharomyces yeasts, promoting the use of these yeasts in association with Saccharomyces cerevisiae. Non-Saccharomyces yeasts contribute to improve wine complexity and organoleptic composition. However, the use of mixed starters needs to better understand the effect of the interaction between these species during alcoholic fermentation. The aim of this study is to evaluate the influence of mixed starter cultures, composed by combination of different S. cerevisiae and Hanseniaspora uvarum strains, on wine characteristics and to investigate the role of cell-to-cell contact on the metabolites produced during alcoholic fermentation. In the first step, three H. uvarum and two S. cerevisiae strains, previously selected, were tested during mixed fermentations in natural red grape must in order to evaluate yeast population dynamics during inoculated fermentation and influence of mixed starter cultures on wine quality. One selected mixed starter was tested in a double-compartment fermentor in order to compare mixed inoculations of S. cerevisiae/H. uvarum with and without physical separation. Our results revealed that physical contact between S. cerevisiae and H. uvarum affected the viability of H. uvarum strain, influencing also the metabolic behaviour of the strains. Although different researches are available on the role of cell-to-cell contact-mediated interactions on cell viability of the strains included in the mixed starter, to our knowledge, very few studies have evaluated the influence of cell-to-cell contact on the chemical characteristics of wine.     

葡萄酒高级醇检测方法的优化及其在本土酿酒酵母筛选中的应用

该研究在国标GB/T 5009.48—2003《蒸馏酒与配制酒卫生标准的分析方法》的基础上，建立起一种显色稳定、准确性更高的高级醇检测法。结果表明，当葡萄酒酒样在梯度稀释20倍，加样静置1 min，80 ℃水浴30 min且以50%硫酸溶液作为稀释剂的条件下进行检测，精密度试验结果相对标准偏差（RSD）为1.665%，加标回收率为99.11%，均优于国标法；采用气质联用（GC-MS）法对6株本土酵母产高级醇含量进行对比检测，结果显示所测总量无显著差异（P＞0.05），证明优化法较为准确、可靠。该研究筛选获得了两株低产高级醇菌株LFP529和LFP525，其发酵酒的高级醇含量较对照分别降低了55.44%、58.31%，为解决我国部分产区葡萄酒高级醇含量较高提供了解决方案。