Moving forward sustainable solutions for VOCs biotrickling filtration through co-immobilised microorganisms

This study is moving forward with some available options for upgrading the biotrickling filters (BTFs) treating volatile organic compounds (VOCs) in air, in the light of lowering their greenhouse gas(GHG) emissions. One of such options refers to the addition of the microalgae component to the biological matrix involved in such systems, by (co)immobilization, for the capture of the carbon dioxide issued from the VOCs biodegradation and potentially contributing to the overall VOCs removal performance. Particularly, alginate beads with (co) immobilized microorganisms (microorganisms isolated from commercial compost and microalgae Arthrospira platensis PCC 8005) are for the first time tested for this purpose, as follows: beads with entrapped compost-based microorganisms and attached microalgae (BTF-I); beads with an entrapped mixture of microalgae and compost-based microorganisms (BTF-II). Although both options provided promising performances in treating air contaminated with ethanol (as a model VOC in this study), the last option exhibited lower CO2 emissions and higher packing bed durability, being more prone to further development and implementation.

Addition of disaccharides and dimethyl sulfoxide to sodium alginate gel improves viability of immobilized Saccharomyces boulardii after cryopreservation

Gel-immobilized microorganisms are increasingly used in microbiological industries. Currently, the problem of developing technologies for long-term storage of microorganisms immobilized in gel carriers remains urgent. Low-temperature storage is the most effective method of preserving microorganisms. The viability of immobilized cells is affected by cryoprotective properties of gel matrix as well as cooling regimes. Therefore, the effects of incorporation of cryoprotective agents in alginate gel and cooling regimes on the viability of immobilized Saccharomyces boulardii cells after cryopreservation were studied. Incorporation of non-permeable cryoprotectants (sucrose, lactose, and trehalose) and permeable one dimethyl sulfoxide (DMSO) in alginate gel beads promoted an increase in the viability of immobilized cells after freeze-thawing. The highest viability rates of the gel-immobilized cells were observed in the alginate gel beads incorporating combinations of DMSO (5 – 10 % v/v) and one of the disaccharides (10 – 20 % w/v). In all experiments, slow cooling provided significantly higher viability if compared to the rapid immersion of the samples into liquid nitrogen.

VIABILITY OF PROBIOTIC STRAINS OF MICROORGANISMS AND THEIR ADHESION TO HUMAN ERYTHROCYTES AFTER IMMOBILIZATION IN ALGINATE GEL AND STORAGE AT DIFFERENT LOW TEMPERATURES

The research was focused on the development of technologies for long-term storage of probiotics immobilized in gel carriers at various low temperatures. The aim of the research was to investigate the viability and adhesive activity of probiotic microorganisms after immobilization in an alginate gel and storage at various low temperatures for 24 months (observation period). Probiotic strains of the microorganisms Escherichia coli M–17 (E. coli M–17), Lactobacillus acidophilus IMB B-2637 (L. acidophilus), Saccharomyces cerevisiae IMB Y-505 (S. cerevisiae) were immobilized in 1% alginate gel either without additives or supplemented with lactose, sucrose, skimmed milk and protective SML medium. The samples were frozen at uncontrolled cooling rates in refrigerators with temperatures of –20, –40, –75 °C. When then frozen down to –196 °C, the samples were cooled to –40 °C at the rate of 1 deg / min, and then immersed in liquid nitrogen. The samples were stored at the indicated temperatures for 24 months (observation period). During storage, part of the granules was thawed in a water bath and dissolved in 4% EDTA solution. The viability of microorganisms was determined by the ability of microbial cells to form colonies on agar media. Adhesive activity was determined by the ability to adhere to human erythrocytes 0(I) group, Rh (+). When cooled down to –20, –40, –75, –196 °C and after subsequent storage at –196 °C, immobilized microorganisms in all varieties of gel did not die. In most samples cells died between 1 and 3 months of storage at –20, –40, –75 °C. After 24 months, it was found that the most resistant to storage at these temperatures were the bacteria L. acidophilus, and the most sensitive were the yeast S. cerevisiae. The viability of all microorganisms immobilized in 1% gel without additives was minimal. The addition of disaccharides of lactose, sucrose, SML medium and milk to the alginate gel increased the cryoprotective properties of the alginate gel. The highest viability of immobilized microorganisms was observed in the gel with SML medium. As the storage temperature decreased from –20 to –75 °C, the number of viable microbial cells in all gel samples increased. Immobilization in gel carriers and storage for 24 months did not affect the adhesive properties of probiotics E. coli M–17, L. acidophilus, S. cerevisiae. The changes in the viability of microbial cells are associated with the severity of damaging physicochemical factors that accompany the processes of water crystallization at temperatures of –20, –40, –75 °C. The protective effect of additives in the composition of the alginate gel is analyzed. The viability of microorganisms immobilized in gel granules during long-term storage at different low temperatures is influenced by the species cryoresistance of microorganisms, temperature regimens and storage duration, the composition of the gel carrier. The processes of immobilization and storage at low temperatures did not change the adhesive activity of immobilized microorganisms.

Suitability of Immobilized Systems for Microbiological Degradation of Endocrine Disrupting Compounds

The rising pollution of the environment with endocrine disrupting compounds has increased interest in searching for new, effective bioremediation methods. Particular attention is paid to the search for microorganisms with high degradation potential and the possibility of their use in the degradation of endocrine disrupting compounds. Increasingly, immobilized microorganisms or enzymes are used in biodegradation systems. This review presents the main sources of endocrine disrupting compounds and identifies the risks associated with their presence in the environment. The main pathways of degradation of these compounds by microorganisms are also presented. The last part is devoted to an overview of the immobilization methods used for the purposes of enabling the use of biocatalysts in environmental bioremediation.

Valorization of Agro-Industrial By-products: Use of Rice Husk as a Source of Microorganisms to Denitrification of Water

Rice husk, which is an agricultural waste, provides a feasible alternative for the growth and propagation of denitrifying microorganisms. Nitrate and nitrite were removed using Immobilized Microorganisms (MOIM) or Microorganisms in Solution (MOSO). Microorganisms present in the rice husk biomass responsible for denitrification were identified as Pseudomonas, and other microorganisms have also been identified, as Oerskovia spp. Enterococcus sp. Bacillus mycoides and Escherichia coli. The influence of pH, temperature, C/N ratio and carbon source on biological denitrification were investigated. MOIM and MOSO consortium had optimal denitrifying performance at 25-30 °C and in pH 7-8. MOSO has average denitrification efficiency larger than MOIM. The MOIM denitrification efficiency was more sensitive to pH changes than the MOSO. Ethanol and sodium acetate were carbon sources for the denitrifying process. The efficiency of nitrate and nitrite removal using MOSO and ethanol or acetate with 1:1, 1:2, 1:3 and 1:4 C/N ratios were equivalents and above 97.00%. The denitrifying process presented was robust and it presented nitrate removal close to 100% during 10 cycles.

Field testing of immobilized oil-degrading microorganisms in the Zhanatalap field of Atyrau region

Hydrocarbon-oxidizing microorganisms are widespread in natural ecosystems, since the ability to oxidize hydrocarbons is associated with the presence of enzymes of the oxidase group, with microorganisms using oil and oil products as the sole source of carbon and energy in the microbiological decomposition of hydrocarbons. The decomposition of oil and oil products in the soil under natural conditions is a biogeochemical process in which the functional activity of a complex of soil microorganisms that ensure the complete mineralization of oil and oil products to carbon dioxide and water is of crucial importance. The search for effective indigenous hydrocarbon-oxidizing microorganisms, the creation on their basis of a full-fledged specialized consortium of microorganisms and their introduction into the initial, cleaned environment is one of the promising methods of purification with oil pollution in the oil-producing regions of Kazakhstan. Among the new biological methods for cleaning soil from oil pollution, the most promising are the use of a consortium based on immobilized microorganisms. A correctly selected carrier capable of sorption of petroleum hydrocarbons preserves and maintains attached cells in a viable state for a long time and protects them, especially at the initial stage of introduction, from adverse environmental conditions, which increases the efficiency of oil destruction. Hydrocarbon-oxidizing microorganisms have high emulsifying activity and sorption ability for expanded clay, optimal conditions for biomass accumulation are: temperature 28-30 °С, pH = 7 and 9. It is recommended to use a consortium of oil-degrading microorganisms based on the native strains of cultures Bacillus firmus S20, Bacillus subtilis PR28, Micrococcus roseus UD6-4, Micrococcus varians PR69 to clean the soils contaminated with oil and oil products in the Zhanatalap field in the Atyrau region. It should be noted that after 8 months at the Zhanatalap field in the Atyrau region, oil destruction amounted to 94.3% in the variant with the introduction of immobilized microorganisms on zeolite and expanded clay. The results of the research are the basis for further development of technology for the restoration of oil-contaminated soils in arid conditions of Kazakhstan.

Innovative ex-situ biological biogas upgrading using immobilized biomethanation bioreactor (IBBR)

Biogas, which typically consists of about 50–70% of methane gas, is produced by anaerobic digestion of organic waste and wastewater. Biogas is considered an important energy resource with much potential; however, its application is low due to its low quality. In this regard, upgrading it to natural gas quality (above 90% methane) will broaden its application. In this research, a novel ex-situ immobilized biomethanation bioreactor (IBBR) was developed for biologically upgrading biogas by reducing CO2 to CH4 using hydrogen gas as an electron donor. The developed process is based on immobilized microorganisms within a polymeric matrix enabling the application of high recirculation to increase the hydrogen bioavailability. This generates an increase in the consumption rate of hydrogen and the production rate of methane. This process was successfully demonstrated at laboratory-scale system, where the developed process led to a production of 80–89% methane with consumption of more than 93% of the fed hydrogen. However, a lower methane content was achieved in the bench-scale system, likely as a result of lower hydrogen consumption (63–90%). To conclude, the IBBRs show promising results with a potential for simple and effective biogas upgrading.