Vol 54, No 4 (2018)

The technology of the yeast cell surface display, which appeared 20 years ago and was based on the displaying of target proteins on the cell surface via fusion to an abundant cell wall protein finds broad application in basic and applied research. The main advantage of the cell surface display on the basis of eukaryotic microorganisms—yeast—is the opportunity for correct modification of mammalian proteins. The cell surface display is an important tool for the analysis and understanding of protein function and protein–protein interactions and for the screening of novel clones from peptide and protein libraries. This technology makes it possible to obtain cells with novel abilities, such as catalytic functions and affinity binding to valuable ligands, including rare and heavy metals. It provides the chance to use yeast in biotechnology and in bioremediation and biomonitoring of the environment. The review considers the methods of obtaining a cell surface display on the basis of the yeasts Saccharomyces cerevisiae, Pichia pastoris, and Yarrowia lipolytica, the properties of anchor proteins, and the main fields of yeast display technology.

In the present scenario of depleting oil reservoir, microbial oil has gained much attention over plant and animal based sources. Among different microorganisms, yeast strains are considered superior source for oil production. The cost of oil produced by yeast could further be lowered using cheaper agro-waste and biomass as substrate. This review focuses on key topics which will help in gaining better understanding to enhance lipid production using yeast strains. The effects of oleaginous yeast co-culturing with microalgae, different cheap carbon sources of biomass, and types of yeast species on oil production were highlighted in the review. An overview of mechanisms of oil production from biomass, viz. pretreatment of biomass, fermentation and oil recovery are also provided. Constraints encountered during the oleogenesis or microbial oil accumulation and their probable solutions along with a section on different by-products obtained during oleo-genesis are also discussed.

Chymotrypsin was immobilized as a part of hybrid organo-inorganic nanocomplexes on selenium nanoparticles in the reduction reaction of selenious acid with ascorbic acid. Chymotrypsin stabilized the selenium nanoparticles in the solution. The spectral characteristics of synthesized nanocomplexes and the proteolytic activity of immobilized chymotrypsin were studied. It was shown that the immobilized enzyme had increased proteolytic activity in an alkaline medium.

A novel exo-arabinase (GH93, exo-ABN) enzyme produced by the ascomycete Penicillium canescens has been studied. Cloning of the abn1 gene coding for exo-ABN into the recipient P. canescens strain RN3-11-7 yielded recombinant producing strains characterized by a high yield of extracellular exo- ABN production (20–30% of the total amount of extracellular protein). Chromatographic purification yielded a homogenous exo-ABN with a molecular weight of 47 kDa, as shown by SDS-PAGE. The enzyme showed high specific activity towards linear arabinan (117 U/mg) and low specific activity towards branched arabinan and arabinoxylan (4–5 U/mg) and para-nitrophenyl-α-L-arabinofuranoside (0.3 U/mg), whereas arabinogalactan and para-nitrophenyl-α-L-arabinopyranoside, the substrates that contained the pyranose form of arabinose, were not hydrolyzed. Arabinohexaose was the major product of linear arabinan hydrolysis. Exo-ABN had a pH optimum at 5.0 and a temperature optimum at 60°C. The enzyme was stable in a broad pH range (4.0–7.0) and upon heating to 50°C during 180 min. Extensive hydrolysis of linear and branched arabinans by exo- and endo-arabinase mixtures, arabinofuranosidase, and arabinofuran-arabinoxylan hydrolase has been performed. The degree of substrate conversion amounted to 67 and 83% of the maximal possible value, respectively.

The composition of traditional influenza vaccines require nearly annual updates due to the high variability of the influenza virus. The use of conservative viral antigens, the extracellular domain of the transmembrane protein M2, and fragments of the second subunit of hemagglutinin provides the opportunity to create recombinant broad-spectrum vaccines. Bacterial flagellin was used as a mucosal adjuvant to increase the immunogenicity of these conservative antigens. Recombinant proteins based on flagellin simultaneously containing M2e and a fragment of the hemagglutinin stem region were expressed in Nicotiana benthamiana plants using a self-replicating vector based on the potato virus X genome. Methods for their isolation from plants and purification have been developed. The developed expression system can be used to produce a new candidate influenza vaccine in plants.

Presowing treatment of wheat (Triticum aestivum L.) seeds with 10 or 100 μM salicylic acid (SA) reduced the inhibition of 14-day-old plant growth under soil drought. The same effect was caused by the spraying of 7-day-old seedlings with 0.5 or 2 mM nitrogen oxide donor (sodium nitroprusside, SNP) before drought. The protective effect was enhanced by the combination of seed treatment with 10 μM SA and plant spraying with 0.5 mM SNP, while their combinations in higher concentrations caused weaker effects. SA treatment in both concentrations and 0.5 mM SNP under drought conditions increased the antioxidant enzyme activity (superoxide dismutase, catalase, and guaiacol peroxidase) in leaves. This effect was especially significant when 10 μM SA was combined with 0.5 mM SNP. Spraying with 2 mM SNP and its combination with seed presowing with 100 μM SA did not significantly change the antioxidant enzyme activity; however, the proline content in the leaves increased. It is concluded that the SA stress-protective action on plants can be modified with exogenous nitrogen oxide.

A comparative study of the oxidation of ferrous iron ions by various cultures of acidophilic chemolithotrophic microorganisms in solutions obtained after ferric leaching of copper-zinc concentrate at 80°C has been carried out. It was shown that the use of a moderately thermophilic culture for bioregeneration of leaching solutions was preferable. At the same time, the oxidation rate of Fe²⁺ ions reached 0.88 g/(L h), or 21.1 g/(L day). We propose that the activity of the moderately thermophilic culture was due to the presence of the mixotrophic bacteria Sulfobacillus spp., which used organic products of the microbial lysis for their growth. These products were formed during high-temperature ferric leaching of the copper-zinc concentrate with the biosolution.

Metabolic profiling is a key approach in current basic and applied research in biology. Comparative analysis of different metabolite extraction methods for pea (P. sativum) and black medick (M. lupulina) made it possible to find the optimal conditions for metabolite extraction and subsequent detection by gas chromatography coupled with mass spectrometry. The optimized method was shown to be reliable for assessment of the organ and species metabolic profiles for roots and leaves in pea and black medick plants.