Mathematical Modelling of Canola Oil Biodegradation and Optimisation of Biosurfactant Production by an Antarctic Bacterial Consortium Using Response Surface Methodology

An Antarctic soil bacterial consortium (reference BS14) was confirmed to biodegrade canola oil, and kinetic studies on this biodegradation were carried out. The purpose of this study was to examine the ability of BS14 to produce biosurfactants during the biodegradation of canola oil. Secondary mathematical equations were chosen for kinetic analyses (Monod, Haldane, Teissier–Edwards, Aiba and Yano models). At the same time, biosurfactant production was confirmed through a preliminary screening test and further optimised using response surface methodology (RSM). Mathematical modelling demonstrated that the best-fitting model was the Haldane model for both waste (WCO) and pure canola oil (PCO) degradation. Kinetic parameters including the maximum degradation rate (μmax) and maximum concentration of substrate tolerated (Sm) were obtained. For WCO degradation these were 0.365 min−1 and 0.308%, respectively, while for PCO they were 0.307 min−1 and 0.591%, respectively. The results of all preliminary screenings for biosurfactants were positive. BS14 was able to produce biosurfactant concentrations of up to 13.44 and 14.06 mg/mL in the presence of WCO and PCO, respectively, after optimisation. The optimum values for each factor were determined using a three-dimensional contour plot generated in a central composite design, where a combination of 0.06% salinity, pH 7.30 and 1.55% initial substrate concentration led to the highest biosurfactant production when using WCO. Using PCO, the highest biosurfactant yield was obtained at 0.13% salinity, pH 7.30 and 1.25% initial substrate concentration. This study could help inform the development of large-scale bioremediation applications, not only for the degradation of canola oil but also of other hydrocarbons in the Antarctic by utilising the biosurfactants produced by BS14.

Recombinant Enzymatic Redox Systems for Preparation of Aroma Compounds by Biotransformation

The aim of this study was to develop immobilized enzyme systems that reduce carbonyl compounds to their corresponding alcohols. The demand for natural aromas and food additives has been constantly growing in recent years. However, it can no longer be met by extraction and isolation from natural materials. One way to increase the availability of natural aromas is to prepare them by the enzymatic transformation of suitable precursors. Recombinant enzymes are currently being used for this purpose. We investigated trans-2-hexenal bioreduction by recombinant Saccharomyces cerevisiae alcohol dehydrogenase (ScADH1) with simultaneous NADH regeneration by recombinant Candida boidinii formate dehydrogenase (FDH). In a laboratory bioreactor with two immobilized enzymes, 88% of the trans-2-hexenal was transformed to trans-2-hexenol. The initial substrate concentration was 3.7 mM. The aldehyde destabilized ScADH1 by eluting Zn2+ ions from the enzyme. A fed-batch operation was used and the trans-2-hexenal concentration was maintained at a low level to limit the negative effect of Zn2+ ion elution from the immobilized ScADH1. Another immobilized two-enzyme system was used to reduce acetophenone to (S)-1-phenylethanol. To this end, the recombinant alcohol dehydrogenase (RrADH) from Rhodococcus ruber was used. This biocatalytic system converted 61% of the acetophenone to (S)-1-phenylethanol. The initial substrate concentration was 8.3 mM. All enzymes were immobilized by poly-His tag to Ni2+, which formed strong but reversible bonds that enabled carrier reuse after the loss of enzyme activity.

The Use of Response Surface Methodology as a Statistical Tool for the Optimisation of Waste and Pure Canola Oil Biodegradation by Antarctic Soil Bacteria

Hydrocarbons can cause pollution to Antarctic terrestrial and aquatic ecosystems, both through accidental release and the discharge of waste cooking oil in grey water. Such pollutants can persist for long periods in cold environments. The native microbial community may play a role in their biodegradation. In this study, using mixed native Antarctic bacterial communities, several environmental factors influencing biodegradation of waste canola oil (WCO) and pure canola oil (PCO) were optimised using established one-factor-at-a-time (OFAT) and response surface methodology (RSM) approaches. The factors include salinity, pH, type of nitrogen and concentration, temperature, yeast extract and initial substrate concentration in OFAT and only the significant factors proceeded for the statistical optimisation through RSM. High concentration of substrate targeted for degradation activity through RSM compared to OFAT method. As for the result, all factors were significant in PBD, while only 4 factors were significant in biodegradation of PCO (pH, nitrogen concentration, yeast extract and initial substrate concentration). Using OFAT, the most effective microbial community examined was able to degrade 94.42% and 86.83% (from an initial concentration of 0.5% (v/v)) of WCO and PCO, respectively, within 7 days. Using RSM, 94.99% and 79.77% degradation of WCO and PCO was achieved in 6 days. The significant interaction for the RSM in biodegradation activity between temperature and WCO concentration in WCO media were exhibited. Meanwhile, in biodegradation of PCO the significant factors were between (1) pH and PCO concentration, (2) nitrogen concentration and yeast extract, (3) nitrogen concentration and PCO concentration. The models for the RSM were validated for both WCO and PCO media and it showed no significant difference between experimental and predicted values. The efficiency of canola oil biodegradation achieved in this study provides support for the development of practical strategies for efficient bioremediation in the Antarctic environment.

Evaluating the Performance of Three Chambers Microbial Salinity Cell (MSC) Subjected to Different Substrate Concentrations to Accomplish Simultaneous Organic and Salt Removal in the Wastewater

This study aimed to identify the effect of substrate concentration on the performance of A Three chambers Microbial Salinity Cell (a three chambers MSC). In this study, 3 three chambers MSC was made of plexy glass with total volume of 200 ml. Alumunium wrapped with with platinum on vulcan carbon cloth were used as electrodes,with each working area 63 cm2. The results showed that a Three chambers Microbial Salinity Cell was able to generate electricity and at the same time removed salinity. The degree of electricity deneration and salinity removal were influenced by initial substrate concentration in the anode chamber. The higher substrate concentration, the better performance of MSC. The best performance of MSC achieved when COD was 2034 mg/L, resulted in maximum voltage of 0. 44 V, and maximum current density of 0.29 mA/m2. With % CE was 5.4%. The maximum conductivity increase in salinity chamber was from 11.2 µS/cm to 1027 µS/cm (salinity 0.57% ppt).

OXIDATION OF ORGANIC COMPOUNDS BY MAGNETIC BIOCATALYST

В статье описывается синтез магнитного биокатализатора на основе иммобилизованной пероксидазы. Данный биокатализатор тестировался в реакции окисления 2,3,6-триметилфенола с помощью пероксида водорода до 2,3,5-триметилгидрохинона (полупродукта витамина Е). В работе выбран метод синтеза магнитных наночастиц. Подобраны оптимальные условия проведения процесса окисления 2,3,6-триметилфенола в присутствии магнитного биокатализатора (начальная концентрация субстрата, температура, рН). The article describes the synthesis of a magnetic biocatalyst based on immobilized peroxidase. This biocatalyst was tested in the oxidation reaction of 2,3,6-trimethylphenol with hydrogen peroxide to 2,3,5-trimethylhydroquinone (an intermediate of vitamin E). In the work, the method of synthesis of magnetic nanoparticles is selected.The optimal conditions for the process of oxidation of 2,3,6-trimethylphenol in the presence of a magnetic bio-catalyst are selected (initial substrate concentration, temperature, pH).

Modeling Power Generation and Energy Efficiencies in Air-Cathode Microbial Fuel Cells Based on Freter Equations

The model proposed in this study was based on the assumption that the biomass attached to the anode served as biocatalysts for microbial fuel cell (MFC) exoelectrogenesis, and this catalytic effect was quantified by the exchange current density of anode. By modifying the Freter model and combining it with the Butler–Volmer equation, this model could adequately describe the processes of electricity generation, substrate utilization, and the suspended and attached biomass concentrations, at both batch and continuous operating modes. MFC performance is affected by the operating variables such as initial substrate concentration, external resistor, influent substrate concentration, and dilution rate, and these variables were revealed to have complex interactions by data simulation. The external power generation and energy efficiency were considered as indices for MFC performance. The simulated results explained that an intermediate initial substrate concentration (about 100 mg/L under this reactor configuration) needed to be chosen to achieve maximum overall energy efficiency from substrate in the batch mode. An external resistor with the value approximately that of the internal resistance, boosted the power generation, and a resistor with several times of that of the internal resistance achieved better overall energy efficiency. At continuous mode, dilution rate significantly impacted the steady-state substrate concentration level (thus substrate removal efficiency and rate), and attached biomass could be fully developed when the influent substrate concentration was equal to or higher than 100 mg/L at any dilution rate of the tested range. Overall, this relatively simple model provided a convenient way for evaluating and optimizing the performance of MFC reactors by regulating operating parameters.

Why is the hydrolytic activity of acetylcholinesterase pH dependent? Kinetic study of acetylcholine and acetylthiocholine hydrolysis catalyzed by acetylcholinesterase from electric eel

The dependence of the activity of acetylcholinesterase from electric eel at a pH value range of 4.8–9.8 (phosphate buffer), regarding acetylcholine and acetylthiocholine hydrolysis, was determined at 25 °C, ionic strength of 0.11 M, and initial substrate concentration of 4 mM. At a pH range of 4.8–9.8, the dependencesA(pH) form a sigmoid increasing curve with the maximum catalytic activity at a pH range 8–9.5. For acetylcholine hydrolysis, the kinetic reason for such an increase inAconsists mainly of an increase in the rate constantk2(Michaelis-Menten) model with increasing pH of the reaction mixture. For acetylthiocholine hydrolysis, the kinetic explication of the determined dependenceA(pH) is more complicated.

Modeling Power Generation and Energy Efficiencies in Air-Cathode Microbial Fuel Cells Based on Freter Equations

The model proposed in this study was based on the assumption that the biomass attached to the anode served as biocatalysts for MFC exoelectrogenesis, and this catalytic effect was quantified by the exchange current density of anode. By modifying the Freter model and combining it with the Butler-Volmer equation, this model could adequately describe the processes of electricity generation, substrate utilization, and the suspended and attached biomass concentrations, at both batch and continuous operating modes. MFC performance is affected by the operating variables such as initial substrate concentration, external resistor, influent substrate concentration, and dilution rate, and these variables were revealed to have complex interactions by data simulation. The external power generation and energy efficiency were considered as indices for MFC performance. The simulated results explained that an intermediate initial substrate concentration (about 100 mg/L under this reactor configuration) needed to be chosen to achieve maximum overall energy efficiency from substrate in the batch mode. An external resistor with the value about that of the internal resistance boosted the power generation, and a resistor with several times of that of the internal resistance achieved better overall energy efficiency. At continuous mode, dilution rate significantly impacted the steady-state substrate concentration level (thus substrate removal efficiency and rate), and attached biomass could be fully developed when the influent substrate concentration was equal to or higher than 100 mg/L at any dilution rate of the tested range. Overall, this relatively simple model provided a convenient way for evaluating and optimizing the performance of MFC reactors by regulating operating parameters.