Enhancing the performance of brewing yeasts

Beer production is one of the oldest known traditional biotechnological processes, but is nowadays facing increasing demands not only for enhanced product quality, but also for improved production economics. Targeted genetic modification of a yeast strain is one way to increase beer quality and to improve the economics of beer production. In this review we will present current knowledge on traditional approaches for improving brewing strains and for rational metabolic engineering. These research efforts will, in the near future, lead to the development of a wider range of industrial strains that should increase the diversity of commercial beers.     

Efficiency of lipid synthesis by yeasts

The efficiency of lipid synthesis by ethanol-grown yeasts is characterized using the coefficient of the lipid energetic yield (eta(1)). This coefficient is defined as the fraction of energy in an organic substrate that is converted to lipids. The advantages of eta(1) compared with the "fat coefficient" (F(s)) as well as the biomass energetic yield (eta) compared with Y(s) are discussed.     

Synthesis of magneto-sensitive iron-containing nanoparticles by yeasts

Industrial production of magneto-sensitive nanoparticles, which can be used in the production of target drug delivery carriers, is a subject of interest for biotechnology and microbiology. Synthesis of these nanoparticles by microorganisms has been described only for bacterial species. At the same time, it is well known that yeasts can form various metal-containing nanoparticles used, for instance, in semiconductors, etc. This paper describes the first results of the biosynthesis of magneto-sensitive nanoparticles by yeasts. The organisms we used—Saccharomyces cerevisiae and Cryptococcus humicola—represented two different genera. Magneto-sensitive nanoparticles were synthesized at room temperature in bench-scale experiments. The study included transmission electron microscopy of the yeast cells and their energy dispersive spectrum analyses and revealed the presence of iron-containing nanoparticles. Both yeast cultures synthesized nanoparticles at high concentrations of dissolved iron. Electron microscopy showed that nanoparticles were associated mainly with the yeast cell wall. Formation of magneto-sensitive nanoparticles was studied under conditions of applied magnetic fields; a possible stimulating role of magnetic field is suggested. On the whole, the paper reports a novel approach to green biosynthesis of magneto-sensitive nanoparticles.     

A comparative study of the lipid composition of yeasts with different fermentative capacities

Summary The lipid composition of a classical yeast and a poor fermenter, at low and high sugar concentrations, was compared. Polyunsaturated fatty acids (18:2, 18:3) were found in the osmotolerant weak fermenter, Saccharomyces mellis, their content decreasing with an increase of glucose levels, while the highly fermenting yeast S. cerevisiae had no polyunsaturated fatty acids at all sugar concentrations examined. Also total unsaturation of fatty acids ( mol^–1) was significantly higher with S. mellis. The sterol content varied considerably, being higher with the highly fermenting yeasts and low with S. mellis and the film yeast Pichia sp. The ratio of free sterols/phospholipids was high in S. cerevisiae (1:7) and low in S. mellis (1:177). Hybrid yeasts (S. cerevisiaexS. mellis) which were the best fermenting organisms in our study, also showed a high ratio of free sterols/phospholipids (1:6–1:8). A correlation between the fermentative capacity of yeasts and the fluidity of their membranes is suggested.     

Microbial lipid production: screening with yeasts grown on Brazilian molasses

Rhodotorula glutinis CCT 2182, Rhodosporidium toruloides CCT 0783, Rhodotorula minuta CCT 1751 and Lipomyces starkeyi DSM 70296 were evaluated for the conversion of sugars from Brazilian molasses into single-cell oil (SCO) feedstock for biodiesel. Pulsed fed-batch fermentations were performed in 1.65 l working volume bioreactors. The maximum specific growth rate (µ_max), lipid productivity (Pr) and cellular lipid content were, respectively, 0.23 h^?1, 0.41 g l^?1 h^?1, and 41 % for Rsp. toruloides; 0.20 h^?1, 0.27 g l^?1 h^?1, and 36 % for Rta. glutinis; 0.115 h^?1, 0.135 g l^?1 h^?1, and 27 % for Rta. minuta; and 0.11 h^?1, 0.13 g l^?1 h^?1, and 32 % for L. starkeyi. Based on their microbial lipid productivity, content, and profile, Rsp. toruloides and Rta. glutinis are promising candidates for biodiesel production from Brazilian molasses. All the oils from the yeasts were similar to the composition of plant oils (rapeseed and soybean) and could be used as raw material for biofuels, as well as in food and nutraceutical products.     

Determination of iron in saccharomycete yeasts by the dipyridyl method

Iron content in intact yeast cells without their incineration or disintegration can be determined using 2,2'-dipyridyl.     

Isolation and characteristics of the lipid granules of Candida tropicalis yeasts

Preparative isolation of lipid granules from the protoplasts of Candida tropicalis was conducted by a technique of flotation in a stepwise density gradient. Parameters were selected for decomposing the protoplasts under hypotonic and isotonic conditions which made it possible to preserve the lipid granules being isolated intact, as well as parameters of a density gradient and centrifugation. The specific content of lipids, proteins and low molecular weight compounds was assayed using labeled compounds in the lipid granules which were isolated from yeast cells cultivated on various carbon substrates (1-6(-14C)-glucose and 1(-14C-octadecane). The lipid composition of the spherosomes was determined. If the yeast was grown on glucose, lipids localized in the lipid granules were represented mainly by triglycerides whose carbon constituted 69 per cent of the total lipid carbon. If it was cultivated on n-octadecane, these lipids were represented by hydrocarbons (51 per cent) and triglycerides (22 per cent). The structures isolated possessed a small lipase activity. The specific lipase activity of the lipid granules was lower by 16 per cent than that of the cell protoplast.     

脂质纳米粒子在药物中的应用

脂质纳米粒子是用生物可降解的脂质制备,故这种载体系统拥有很好的生物相容性和安全性。本文着重介绍脂质纳米粒子在药物中的应用,如抗肿瘤药物、抗病毒药物、抗炎症药物、免疫药物、抗真菌药物、降血糖药物等。最后,指出了脂质纳米粒子的发展前景。     

Sec14 family of lipid transfer proteins in yeasts

The hydrophobicity of lipids prevents their free movement across the cytoplasm. To achieve highly heterogeneous and precisely regulated lipid distribution in different cellular membranes, lipids are transported by lipid transfer proteins (LTPs) in addition to their transport by vesicles. Sec14 family is one of the most extensively studied groups of LTPs. Here we provide an overview of Sec14 family of LTPs in the most studied yeast Saccharomyces cerevisiae as well as in other selected non-Saccharomyces yeasts—Schizosaccharomyces pombe, Kluyveromyces lactis, Candida albicans, Candida glabrata, Cryptococcus neoformans, and Yarrowia lipolytica. Discussed are specificities of Sec14-domain LTPs in various yeasts, their mode of action, subcellular localization, and physiological function. In addition, quite few Sec14 family LTPs are target of antifungal drugs, serve as modifiers of drug resistance or influence virulence of pathologic yeasts. Thus, they represent an important object of study from the perspective of human health.     

Enhancing the efficiency of a PCR using gold nanoparticles

We found that the PCR could be dramatically enhanced by Au nanoparticles. With the addition of 0.7 nM of 13 nm Au nanoparticles into the PCR reagent, the PCR efficiency was increased. Especially when maintaining the same or higher amplification yields, the reaction time could be shortened, and the heating/cooling rates could be increased. The excellent heat transfer property of the nanoparticles should be the major factor in improving the PCR efficiency. Different PCR systems, DNA polymerases, DNA sizes and complex samples were compared in this study. Our results demonstrated that Au nanoparticles increase the sensitivity of PCR detection 5- to 10-fold in a slower PCR system (i.e. conventional PCR) and at least 10⁴-fold in a quicker PCR system (i.e. real-time PCR). After the PCR time was shortened by half, the 100 copies/µl DNA were detectable in real-time PCR with gold colloid added, however, at least 10⁶ copies/µl of DNA were needed to reach a detectable signal level using the PCR reagent without gold colloid. This innovation could improve the PCR efficiency using non-expensive polymerases, and general PCR reagent. It is a new viewpoint in PCR, that nanoparticles can be used to enhance PCR efficiency and shorten reaction times.     

Survey of nonconventional yeasts for lipid and hydrocarbon biotechnology

Nonconventional yeasts have an untapped potential to expand biotechnology and enable process development necessary for a circular economy. They are especially convenient for the field of lipid and hydrocarbon biotechnology because they offer faster growth than plants and easier scalability than microalgae and exhibit increased tolerance relative to some bacteria. The ability of industrial organisms to import and metabolically transform lipids and hydrocarbons is crucial in such applications. Here, we assessed the ability of 14 yeasts to utilize 18 model lipids and hydrocarbons from six functional groups and three carbon chain lengths. The studied strains covered 12 genera from nine families. Nine nonconventional yeasts performed better than Saccharomyces cerevisiae, the most common industrial yeast. Rhodotorula toruloides, Candida maltosa, Scheffersomyces stipitis, and Yarrowia lipolytica were observed to grow significantly better and on more types of lipids and lipid molecules than other strains. They were all able to utilize mid- to long-chain fatty acids, fatty alcohols, alkanes, alkenes, and dicarboxylic acids, including 28 previously unreported substrates across the four yeasts. Interestingly, a phylogenetic analysis showed a short evolutionary distance between the R. toruloides, C. maltosa, and S. stipitis, even though R. toruloides is classified under a different phylum. This work provides valuable insight into the lipid substrate range of nonconventional yeasts that can inform species selection decisions and viability of lipid feedstocks.     

Enhancing the productivity of hybrid yellow-poplar and hybrid sweetgum embryogenic cultures

Summary High-frequency embryogenesis systems were established for hybrid yellow-poplar (Liriodendron tulipifera×L. chinense) and hybrid sweetgum (Liquidambar styraciflua×L. formosana) by modifying a medium originally developed for embryogenic yellow-poplar cultures. Embryogenic cultures of both hybrids, consisting of proembryogenic masses (PEMs), were initiated from immature hybrid seeds on an induction-maintenance medium (IMM) supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D), benzyladenine (BA), and casein hydrolyzate (CH). For hybrid yellow-poplar, as many as 2100 germinable somatic embryos per 4000 cells or cell clumps were produced when PEMs were grown in liquid IMM lacking CH, at a pH that varied with genotype (3.5 or 5.6), followed by size fractionation and plating on semisolid embryo development medium (DM; IMM lacking 2,4-D and BA) without CH, but supplemented with 4.0 mgl⁻¹ (15 μM) abscisic acid. For hybrid sweetgum, up to 1650 germinable somatic embryos per 4000 cells or cell clumps were produced when PEMs were grown in liquid IMM without CH, but with 550 mgl⁻¹ l-glutamine, 510 mg l⁻¹ asparagine, and 170 mg l⁻¹ arginine at pH 5.6. Somatic embryos developed from cell clumps on DM without any plant growth regulators or other supplements. Hundreds of somatic embryos of both hybrids were germinated on DM without CH, transferred to potting mix, and hardened off in a humidifying chamber for transfer to the greenhouse.     

Daily supplementation with iron increases lipid peroxidation in young women with low iron stores

The aim of this study was to determine whether women with low iron stores (plasma ferritin 相似文献