O. V. Senko

Production of biofuels from pretreated microalgae biomass by anaerobic fermentation with immobilized Clostridium acetobutylicum cells.

The purpose of this work was to study the possible use of pretreated biomass of various microalgae and cyanobacteria as substrates for acetone-butanol-ethanol (ABE) fermentation by Clostridium acetobutylicum cells immobilized into poly(vinyl alcohol) cryogel. To this end, the biochemical composition of photosynthetic microorganisms cultivated under various conditions was studied. The most efficient technique for pretreating microalgal biomass for its subsequent conversion into biofuels appeared to be thermal decomposition at 108 °C. For the first time the maximum productivity of the ABE fermentation in terms of hydrogen (8.5 mmol/L medium/day) was obtained using pretreated biomass of Nannochloropsis sp. Maximum yields of butanol and ethanol were observed with Arthrospira platensis biomass used as the substrate. Immobilized Clostridium cells were demonstrated to be suitable for multiple reuses (for a minimum of five cycles) in ABE fermentation for producing biofuels from pretreated microalgal biomass.

Biocatalysts Based on Immobilized Cells of Microorganisms in the Production of Bioethanol and Biobutanol

In this work, we discuss the processes for the production of bioethanol and biobutanol, which are promising alternative fuels, using biocatalysts based on cells of various microorganisms immobilized in poly(vinyl alcohol) cryogel. Biocatalysts based on immobilized cells reliably allow ethanol production from a variety of industrial and agricultural wastes (wheat straw, beet and sugarcane bagasse, parchment, corn cobs, soybean processing waste) with a high degree of conversion of consumed substrates to the target product. Ethanol concentrations are appreciably higher in media with biocatalysts than in free cells of the same microorganisms. It is found that immobilized cells of filamentous fungi can convert a wider range of the sugars contained in processed media to ethanol than commonly used yeasts. It is shown that the immobilization of the genus Clostridium cells that produce butanol enables us to reliably change the ratio of solvents that accumulate in the medium during acetone-butanol-ethanol fermentation in the direction of a greater amount of butanol, thereby improving the process’s characteristics relative to present-day technologies based on free bacterial cells.

Biosensitive element in the form of immobilized luminescent photobacteria for detecting ecotoxicants in aqueous flow-through systems.

We demonstrated the possibility of long-term and efficient application of a biosensitive element (BE) in the form of Photobacterium phosphoreum photobacteria immobilized in poly(vinyl alcohol) (PVA) cryogel for detecting various ecotoxicants (Zn(2) (+) , Cu(2) (+) , Hg(2) (+) , Pb(2) (+) , 2,4-dichlorophenoxyacetic acid, 2,6-dimethylphenol, pentachlorophenol, coumaphos, malathion, chlorpyrifos and methyl parathion) in flow-through media. The range of detectable concentrations of ecotoxicants was determined at 1 × 10(-8) to 1 × 10(-4) M for heavy metal ions and at 1 × 10(-8) to 1 × 10(-5) M for phenol derivatives and organophosphorus pesticides. Immobilized cells of photobacteria quantitatively reacted with these ecotoxicants; cell sensitivity exhibited no flow rate dependence in the range from 45 to 180 mL/h. At a constant concentration of ecotoxicant in the flow, the bioluminescence quenching profile of immobilized cells demonstrated an integral response. The BE could remain in a flow-through medium for at least 10 days while retaining 95% of luminescent activity in the absence of ecotoxicants. The BE tested in this work was demonstrated to have a long shelf life (> 60 weeks) at -80°C without changes in the baseline level of bioluminescence. Copyright

Immobilized fungal biocatalysts for the production of cellulase complex hydrolyzing renewable plant feedstock

We discuss characteristics of the directional formation of samples of heterogeneous biocatalysts based on immobilized cells of different microscopic fungi that are characterized by high productivity of cellulases with different substrate specificities (endoglucanases, exoglucanases, and beta-glucosidases). Samples of immobilized cells characterized by maximum productivity of the enzymes of cellulase complex are selected based on our study of the catalytic and operating characteristics of the designed biocatalysts. It is found that a biocatalyst based on Aspergillus terreus spores immobilized in polyvinyl alcohol cryogel is the best of the ones available. It is shown for the first time that the developed biocatalyst retains a high level of productivity for the full complex of cellulases when using various substrate inducers of enzyme biosynthesis, such as birch and oak sawdust, and rice and wheat straw. We demonstrate the possibility of efficiently using cellulase complexes obtained as a result of the functioning of immobilized cells in the saccharification of various cellulose-containing agricultural wastes and the conversion of the obtained sugars to organic solvents (ethanol, butanol) considered to be promising alternative fuels. The concentrations of organic solvents in media with immobilized cells are considerably higher than those found for free cells of the same microorganisms.

Complex effect of lignocellulosic biomass pretreatment with 1-butyl-3-methylimidazolium chloride ionic liquid on various aspects of ethanol and fumaric acid production by immobilized cells within SSF

The pretreatment of softwood and hardwood samples (spruce and hornbeam wood) with 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) was undertaken for further simultaneous enzymatic saccharification of renewable non-food lignocellulosic biomass and microbial fermentation of obtained sugars to ethanol and fumaric acid. A multienzyme cocktail based on cellulases and yeast or fungus cells producing ethanol and fumaric acid were the main objects of [Bmim]Cl influence studies. A complex effect of lignocellulosic biomass pretreatment with [Bmim]Cl on various aspects of the process (both action of cellulases and microbial conversion of hydrolysates to target products) was revealed. Positive effects of the pretreatment with [Bmim]Cl included decreasing the lignin content in the biomass, and increasing the effectiveness of enzymatic hydrolysis and microbial transformation of pretreated biomass. Immobilized cells of both yeasts and fungi possessed improved productive characteristics in the biotransformation of biomass pretreated with [Bmim]Cl to ethanol and fumaric acid.

Optimization of the Use of His6-OPH-Based Enzymatic Biocatalysts for the Destruction of Chlorpyrifos in Soil

Applying enzymatic biocatalysts based on hexahistidine-containing organophosphorus hydrolase (His6-OPH) is suggested for the decomposition of chlorpyrifos, which is actively used in agriculture in many countries. The application conditions were optimized and the following techniques was suggested to ensure the highest efficiency of the enzyme: first, the soil is alkalinized with hydrated calcitic lime Ca(OH)2, then the enzyme is introduced into the soil at a concentration of 1000 U/kg soil. Non-equilibrium low temperature plasma (NELTP)-modified zeolite is used for immobilization of the relatively inexpensive polyelectrolyte complexes containing the enzyme His6-OPH and a polyanionic polymer: poly-l-glutamic acid (PLE50) or poly-l-aspartic acid (PLD50). The soil’s humidity is then increased up to 60–80%, the top layer (10–30 cm) of soil is thoroughly stirred, and then exposed for 48–72 h. The suggested approach ensures 100% destruction of the pesticide within 72 h in soils containing as much as 100 mg/kg of chlorpyrifos. It was concluded that using this type of His6-OPH-based enzyme chemical can be the best approach for soils with relatively low humus concentrations, such as sandy and loam-sandy chestnut soils, as well as types of soil with increased alkalinity (pH 8.0–8.4). Such soils are often encountered in desert, desert-steppe, foothills, and subtropical regions where chlorpyrifos is actively used.

Biocatalytic production of extracellular exopolysaccharide dextran synthesized by cells of Leuconostoc mesenteroides

Results are presented from studies and a comparative analysis of the production of the commercially important product dextran from sucrose using fed-batch cultivated cells of the Leuconostoc mesenteroides subsp. dextranicum B-5481 bacterium either immobilized in a polyvinyl alcohol (PVA) cryogel or in the form of a suspension. It is shown that under identical process conditions, the concentration of dextran is 1.2 times higher when using immobilized cells instead of free cells. The high productivity of dextran formation (4.2 g/(L h)) under the conditions of fed-batch cultivation of the immobilized cells and the ability of these cells to function without losing their metabolic activity for at least five operating cycles are demonstrated. The productivity of the developed biocatalyst is 5 times higher than that of Weissella confusa cells immobilized in a calcium alginate gel and 34 times higher than that of Leuconostoc mesenteroides KIBGE HA1 cells immobilized in a polyacrylamide gel. The molecular weight of the dextran samples produced by the immobilized L. mesenteroides B-5481 cells is half that of the polymer produced by the free cells, expanding the range of possible applications of the polysaccharide with no additional hydrolysis.

Production of various organic acids from different renewable sources by immobilized cells in the regimes of separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SFF)

The study was aimed at production of different organic acids (OA) (lactic, fumaric, or succinic) by various microbial cells (filamentous fungi Rhizopus oryzae (F-814, F-1127) and bacteria Actinobacillus succinogenes B-10111) immobilized into poly(vinyl alcohol) (PVA) cryogel from diverse renewable raw materials (wheat and rice straw, aspen and pine sawdust, Jerusalem artichoke stems and tubers, biomass of macro- and microalgae) under batch conditions. The process productivity, bulk output and OA concentrations were higher in case of using immobilized cells than in case of free cells under identical conditions. A higher OA productivity was reached via simultaneous enzymatic saccharification and microbial fermentation (SSF) of same raw materials as compared to their separate enzymatic hydrolysis and fermentation of accumulated reducing sugars (SHF). Maximal concentrations of all OAs studied were obtained for bioconversion of Jerusalem artichoke tubers. The immobilized cells were used in long-term conversion of various renewable materials to OAs in SSF.

Aspartic and glutamic acids polymers: preparation and applications in medicinal chemistry and pharmaceutics

The methods of the fabrication of polymers based on aspartic and glutamic acids as monomers are reviewed. The methods are perspective from the viewpoint of green chemistry and economics. Actual tendencies existing in the application of the polymers in medicinal chemistry and pharmaceutics are also considered. The results of using mentioned polymers of amino acids to obtain stable nanosized enzymatic complex drugs, based on organophosphate hydrolase and possessing both antibacterial and antineurotoxic action are presented. The drugs are effective destructors of N-acyl homoserine lactones, playing the role of signaling molecules for the quorum response of gram-negative bacteria. These enzymatic-polymer complexes in combination with well-known antibiotics reduce antimicrobial doses inhibiting growth of the pathogens.

Highly concentrated populations of Aureobasidium pullulans cells in biocatalytic pullulan production processes

Results are presented from studies and a comparative analysis of highly concentrated populations of free and immobilized Aureobasidium pullulans Y-4137 cells in the biocatalytic processes of pullulan production in glucose-containing media. The possibility of effectively using the developed biocatalyst in the form of immobilized cells is demonstrated. The process characteristics are determined for pullulan production from hydrolysates of various sources of renewable feedstocks (Jerusalem artichoke tubers, aspen wood, Chlorella vulgaris microalgal biomass, and potato pulp) under the action of the catalyst. It is established that A. pullulans cells immobilized in a polyvinyl alcohol (PVA) cryogel consume glucose 1.5 times faster and accumulate a 1.7 times higher concentration of the target polysaccharide in the medium than free cells. The immobilized cells can function for at least 15 operating cycles with a slight (no more than 10%) reduction in their metabolic activity. Analysis of the obtained data confirms that cell immobilization in a PVA gel for the production of pullulan allows us to shorten the duration of operating cycles in similar processes by a factor of 1.4 while reaching a comparable yield of the target product.