Biocompatible Silica-Polyethylene Glycol-Based Composites for Immobilization of Microbial Cells by Sol-Gel Synthesis.

Biocatalysts based on the methylotrophic yeast Ogataea polymorpha VKM Y-2559 immobilized in polymer-based nanocomposites for the treatment of methanol-containing wastewater were developed. The organosilica composites with different matrix-to-filler ratios derived from TEOS/MTES in the presence of PEG (SPEG-composite) and from silicon-polyethylene glycol (STPEG-composite) differ in the structure of the silicate phase and its distribution in the composite matrix. Methods of fluorescent and scanning microscopy first confirmed the formation of an organosilica shell around living yeast cells during sol-gel bio-STPEG-composite synthesis. Biosensors based on the yeast cells immobilized in STPEG- and SPEG-composites are characterized by effective operation: the coefficient of sensitivity is 0.85 ± 0.07 mgO2 × min-1 × mmol-1 and 0.87 ± 0.05 mgO2 × min-1 × mmol-1, and the long-term stability is 10 and 15 days, respectively. The encapsulated microbial cells are protected from UV radiation and the toxic action of heavy metal ions. Biofilters based on the developed biocatalysts are characterized by high effectiveness in the utilization of methanol-rich wastewater-their oxidative power reached 900 gO2/(m3 × cycle), and their purification degree was up to 60%.

Impact of hydrophilic polymers in organosilica matrices on structure, stability, and biocatalytic activity of immobilized methylotrophic yeast used as biofilter bed.

The impact of hydrophilic polymers in an organosilica matrix on the features and performance of immobilized methylotrophic yeast cells used as biocatalysts was investigated and described. Yeast cells were immobilized in a matrix made of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) by one-step sol-gel route of synthesis in the presence of polyethylene glycol (PEG) or polyvinyl alcohol (PVA). Organosilica shells were spontaneously built around cells as a result of yeast immobilization at a TEOS to MTES ratio of 85/15 vol% and hydrophilic polymer (PEG or PVA). As a structure-directing agent, PVA produces organosilica films. Stable high-performance biocatalysts active for one year, if stored at -18 °C, have been obtained by entrapment of methylotrophic yeast cells. A trickling biofilter with and without active aeration was designed using entrapped yeast cells to treat methanol polluted wastewater. A biofilter model with active aeration could halve methanol input thus demonstrating better performance compared to treatment without active aeration.

A kinetic approach to the formation of two-mediator systems for developing microbial biosensors as exemplified by a rapid biochemical oxygen demand assay.

This work proposes a method of forming a microorganism-mediator(s) receptor system, in which the rates of separate stages of mediator bioelectrocatalysis are used as the basis for the development of biosensors for the biochemical oxygen demand (BOD) rapid assay. In the presence of a ferrocene mediator, the yeast Blastobotrys adeninivorans was shown to enable oxidation of a larger range of substrates as compared with other investigated microorganisms-bacteria Escherichia coli and yeast Ogataea polymorpha. The rate constants of the interaction of the yeast B. adeninivorans with nine compounds, electron transfer mediators, were determined; the best mediator for these microorganisms was found to be neutral red (k int = 0.681 ± 0.009 dm3/g s). Neutral red possesses a high rate of interaction with the ferrocene mediator (14,200 ± 100 dm3/mol s) shown earlier to be the most promising acceptor of electrons at a carbon paste electrode (0.4 ± 0.1 cm/s). These features enabled the formation of a two-mediator ferrocene-neutral red system to be used in a biosensor. A two-mediator-based biosensor had a higher sensitivity (the lower limit of detected BOD concentrations, 0.16 mg/dm3) than that of a one-mediator system based on neutral red and ferrocene. Analysis of ten samples from surface water reservoirs showed the combination of ferrocene, neutral red and the yeast B. adeninivorans to enable the data that highly correlated (R = 0.9693) with those of the standard method.

Three-Dimensional Organization of Self-Encapsulating Gluconobacter oxydans Bacterial Cells.

Self-organized bacteria have been the subject of interest for a number of applications, including the construction of microbial fuel cells. In this paper, we describe the formation of a self-organized, three-dimensional network that is constructed using Gluconobacter oxydans B-1280 cells in a hydrogel consisting of poly(vinyl alcohol) (PVA) with N-vinyl pyrrolidone (VP) as a cross-linker, in which the bacterial cells are organized in a particular side-by-side alignment. We demonstrated that nonmotile G. oxydans cells are able to reorganize themselves, transforming and utilizing PVA-VP polymeric networks through the molecular interactions of bacterial extracellular polysaccharide (EPS) components such as acetan, cellulose, dextran, and levan. Molecular dynamics simulations of the G. oxydans EPS components interacting with the hydrogel polymeric network showed that the solvent-exposed loops of PVA-VP extended and engaged in bacterial self-encapsulation.

Silica sol-gel encapsulated methylotrophic yeast as filling of biofilters for the removal of methanol from industrial wastewater.

This research suggests the use of new hybrid biomaterials based on methylotrophic yeast cells covered by an alkyl-modified silica shell as biocatalysts. The hybrid biomaterials are produced by sol-gel chemistry from silane precursors. The shell protects microbial cells from harmful effects of acidic environment. Potential use of the hybrid biomaterials based on methylotrophic yeast Ogataea polymorpha VKM Y-2559 encapsulated into alkyl-modified silica matrix for biofilters is represented for the first time. Organo-silica shells covering yeast cells effectively protect them from exposure to harmful factors, including extreme values of pH. The biofilter based on the organic silica matrix encapsulated in the methylotrophic yeast Ogataea polymorpha BKM Y-2559 has an oxidizing power of 3 times more than the capacity of the aeration tanks used at the chemical plants during methyl alcohol production. This may lead to the development of new and effective industrial wastewater treatment technologies.

Alteromonas australica sp. nov., isolated from the Tasman Sea.

A non-pigmented, motile, Gram-negative bacterium designated H 17(T) was isolated from a seawater sample collected in Port Phillip Bay (the Tasman Sea, Pacific Ocean). The new organism displayed optimal growth between 4 and 37 °C, was found to be neutrophilic and slightly halophilic, tolerating salt water environments up to 10 % NaCl. Strain H 17(T) was found to be able to degrade starch and Tween 80 but unable to degrade gelatin or agar. Phosphatidylglycerol (27.7 %) and phosphatidylethanolamine (72.3 %) were found to be the only associated phospholipids. The major fatty acids identified are typical for the genus Alteromonas and include C16:0, C16:1ω7, C17:1ω8 and C18:1ω7. The G+C content of the DNA was found to be 43.4 mol%. A phylogenetic study, based on the 16S rRNA gene sequence analysis and Multilocus Phylogenetic Analysis, clearly indicated that strain H 17(T) belongs to the genus Alteromonas. The DNA-DNA relatedness between strain H 17(T) and the validly named Alteromonas species was between 30.7 and 46.4 mol%. Based on these results, a new species, Alteromonas australica, is proposed. The type strain is H 17(T) (= KMM 6016(T) = CIP 109921(T)).