Accumulation of hardly biodegradable plastics such as polyethylene in the environment is a major concern for health and sustainability. Recently, it has been reported that amylase can have a great impact on biodegradation of low-density polyethylene (LDPE)-starch blends. Therefore, biodegradation of such blends can be enhanced in natural media enriched by amylase producing microorganisms. To examine the idea, biodegradation of PE-starch (25 wt LDPE-starch blend was degraded without any pretreatments in a short time. The fertile soil sample rich in amylase producing microorganisms was a proper medium for biodegradation. Molecular weight of polyethylene decreased significantly after four months of treatment. Addition of carbonyl groups to the polymer backbone was a significant step in biodegradation process.

The complexity of the vulcanized rubber makes it difficult to be degraded by microorganisms. It is believed that a microbial consortium can improve the efficiency of the biodegradation process. Fertile soil houses a plethora of microorganisms with innate ability to adapt to various chemical substances come into contact with its texture. Consequently, a soil sample which was in direct contact with tire wastes for more than 13 years was employed in this work to enhance the biodegradation of natural rubber (NR) gloves. The active soil microorganisms associated with the NR latex degradation were isolated and identified using 16S rRNA gene sequencing method. The biodegradation of NR gloves in the soil sample containing these bacteria was investigated and the results represented 87

AbstractPseudomonas putida is a soil bacterium with multiple uses in fermentation and biotransformation processes. P. putida ATCC 12633 can biotransform benzaldehyde and other aldehydes into valuable α‐hydroxyketones, such as (S)‐2‐hydroxypropiophenone. However, poor tolerance of this strain toward chaotropic aldehydes hampers efficient biotransformation processes. To circumvent this problem, we expressed the gene encoding the global regulator PprI from Deinococcus radiodurans, an inducer of pleiotropic proteins promoting DNA repair, in P. putida. Fine‐tuned gene expression was achieved using an expression plasmid under the control of the LacIQ/Ptrc system, and the cross‐protective role of PprI was assessed against multiple stress treatments. Moreover, the stress‐tolerant P. putida strain was tested for 2‐hydroxypropiophenone production using whole resting cells in the presence of relevant aldehyde substrates. P. putida cells harbouring the global transcriptional regulator exhibited high tolerance toward benzaldehyde, acetaldehyde, ethanol, butanol, NaCl, H2O2 and thermal stress, thereby reflecting the multistress protection profile conferred by PprI. Additionally, the engineered cells converted aldehydes to 2‐hydroxypropiophenone more efficiently than the parental P. putida strain. 2‐Hydroxypropiophenone concentration reached 1.6 g L−1 upon a 3‐h incubation under optimized conditions, at a cell concentration of 0.033 g wet cell weight mL−1 in the presence of 20 mM benzaldehyde and 600 mM acetaldehyde. Product yield and productivity were 0.74 g 2‐HPP g−1 benzaldehyde and 0.089 g 2‐HPP g cell dry weight−1 h−1, respectively, 35% higher than the control experiments. Taken together, these results demonstrate that introducing PprI from D. radiodurans enhances chaotrope tolerance and 2‐HPP production in P. putida ATCC 12633.

Aromatic α-hydroxy ketones, such as S-2-hydroxypropiophenone (2-HPP), are highly valuable chiral building blocks useful for the synthesis of various pharmaceuticals and natural products. In the present study, enantioselective synthesis of 2-HPP was investigated by free and immobilized whole cells of Pseudomonas putida ATCC 12633 starting from readily-available aldehyde substrates. Whole resting cells of P. putida, previously grown in a culture medium containing ammonium mandelate, are a source of native benzoylformate decarboxylase (BFD) activity. BFD produced by induced P. putida resting cells is a highly active biocatalyst without any further treatment in comparison with partially purified enzyme preparations. These cells can convert benzaldehyde and acetaldehyde into the acyloin compound 2-HPP by BFD-catalyzed enantioselective cross-coupling reaction. The reaction was carried out in the presence of exogenous benzaldehyde (20 mM) and acetaldehyde (600 mM) as substrates in 6 mL of 200 mM phosphate buffer (pH 7) for 3 h. The optimal biomass concentration was assessed to be 0.006 g dry cell weight (DCW) mL− 1. 2-HPP titer, yield and productivity using the free cells were 1.2 g L− 1, 0.56 g 2-HPP/g benzaldehyde (0.4 mol 2-HPP/mol benzaldehyde), 0.067 g 2-HPP g− 1 DCW h− 1, respectively, under optimized biotransformation conditions (30 °C, 200 rpm). Calcium alginate (CA)–polyvinyl alcohol (PVA)-boric acid (BA)-beads were used for cell entrapment. Encapsulated whole-cells were successfully employed in four consecutive cycles for 2-HPP production under aerobic conditions without any noticeable beads degradation. Moreover, there was no production of benzyl alcohol as an unwanted by-product. Bioconversion by whole P. putida resting cells is an efficient strategy for the production of 2-HPP and other α-hydroxyketones.

The adverse effects of high strength wastewaters on the microbial activities have created a challenge to biological treatments. Microbial fuel cell has been considered as a promising process because the electrical potential generation can stimulate microorganisms and overcome the inhibitory effect. However, several issues (e.g., scalability, high costs and maintenance) have prevented the process from the industrial applications. Elimination of the proton exchange membrane has been suggested as a remedy to the mentioned problems. In this work, a membrane-less microbial fuel cell was modified by putting the cathode within a thin sand layer (instead of the proton exchange membrane) to treat a high strength wastewater sample. The influences of the feed organic load and time of treatment in the modified system were studied in batch and continuous operations. It was revealed that the batch operation efficiency was higher for the lower feed loadings as a 5-day batch treatment removed 66 ± 4% of the 15,000 ± 500 mg/L initial chemical oxygen demand while the continuous process efficiency with 9-day hydraulic residence time was slightly more than 50%. However, the efficiency of the continuous operation for treatment of higher initial loading values was better than the batch mode with the removal efficiency of 41 ± 2% versus 12 ± 2% for a more concentrated leachate feed (45,000 ± 1000 mg/L). Finally, it was disclosed that the modified membrane-less MFC employed in this work can be effective in treatment of high strength wastewaters in larger scales with lower costs.

Costly cofactors such as nicotinamide adenine dinucleotide hydrogen (NADH) are essential to have high activity in many redox enzymatic processes. Cofactor regeneration methods have been suggested to improve the economic aspects of the system. Here, we introduce a microbial electrosynthesis process to regenerate NADH in a two-chamber set-up with Enterobacter aerogenes biofilm as the bio-cathode. The effects of several important factors on the regeneration efficiency were studied and the highest NADH regeneration yield was achieved equal to 65 % at the potential of −1.5 V and the initial NAD+ concentration of 1 mM after 8 h of operation. The regenerated cofactor was highly enzymatically active (93 ± 4 %) which was a great merit of the process. Studying the kinetics of regeneration revealed that the electron transfer rate to the biofilm was the limiting factor. We tried to remove the limitation through co-culturing Pseudomonas aeruginosa and producing more electrochemical active compounds in the biofilm. Although, this modification was not effective for the regeneration yield, it showed that the external potential implicitly influenced the regeneration process by changing the internal microbial cell metabolic fluxes. Finally, it can be concluded that the microbial electrosynthesis is a promising green process for NADH regeneration.

Finding effective drugs to treat SARS-CoV-2 infection as a complementary step to the extensive vaccination is of the great importance to overcome the current pandemic situation. It has been shown that some bio-active unsaturated fatty acids such as Arachidonic Acid (AA) can reduce the infection severity and even destroy the virus by disintegration of the virus lipid envelope. On the other hand, it has been reported that several designed peptides with an activity similar to the angiotensin converting enzyme 2 (ACE-2), which has a high affinity towards the novel corona virus spike protein, can inhibit the viral infection through concealing the spike proteins from the cell surfaces ACE-2. Binding the mentioned peptides to the bio-active lipids like AA will result in a lipopeptide surfactant molecule with the synergistic effect of both the active moieties in its structure to treat the novel corona infection. In addition, the peptide segment increases the aqueous solubility of the lipid segment and enables the targeted delivery of the surfactant molecule to the virus. The resultant lipopeptide would be a potentially effective drug for SARS-CoV-2 infection treatment with the minimum side effects.

It has been suggested that cellulolytic enzymes can be effective on the degradation of PLA samples. The idea was investigated by examining the impact of cellulase on degradation of PLA and PLA-jute (64/36) composite in an aqueous medium. The obtained results demonstrated 55% and 61% thickness reduction in PLA and PLA-jute specimens after four months of treatment, respectively. Gel permeation chromatography (GPC) showed significant decline in the number average molecular weight (Mn) approximately equal to 85% and 80% for PLA and PLA-jute in comparison with their control. The poly dispersity index (PDI) of PLA and PLA-jute declined 41% and 49% that disclosed more homogenous distribution in molecular weight of the polymer after treatment with cellulase. The cellulase promiscuity effect on PLA degradation was further revealed by Fourier-transform infrared spectroscopy (FT-IR) analysis where substantial decrease in the peak intensities of the polymer related functional groups were observed. In addition, PLA biodegradation was studied in more detail by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) of control and cellulase treated specimens. The obtained results confirmed the promiscuous function of cellulase in the presence or the absence of jute as the specific substrate of cellulase. This can be considered as a major breakthrough to develop effective biodegradation processes for PLA products at the end of their life cycle.

The biodegradation of PLA and PLA-Jute (64/36) in an aqueous media with Aspergillus flavus CCUG 28296, as well as its cell-free enzyme extract, was investigated through their physical, molecular, and thermal characterization. Results indicated that the thicknesses of the fungal treated PLA and PLA-jute samples during seven months have reduced by 52% and 63%, respectively while for the enzyme-treated samples, 45% and 49% reduction in the thickness has occurred. Moreover, the gel permeation chromatography (GPC) revealed a substantial decrease (about 75%) in the weight average molecular weight (Mw) of PLA and PLA-Jute treated with fungus, which confirmed the effective performance of A. flavus on the biological degradation of PLA. The obtained results were further supported by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) of the treated and control samples as well. Interestingly, the observed reduction in the Mw of PLA in PLA-Jute was 64% after the enzymatic treatment, while for the unblended PLA, it was just about 32%. These results pointed to the synergistic effect of jute on PLA degradation because of the promiscuous activity of the effective enzymes on jute degradation, which could accelerate the PLA decomposition. (C) 2020 Elsevier Ltd. All rights reserved.

The presence of indigenous microorganisms in the petroleum reservoirs with the capability of biosurfactants production implies the existence of significant amounts of biosurfactants dissolved in the reservoir crude oil. The extraction of these biosurfactants to the aqueous phase can be considered as a promising microbial enhanced oil recovery process in a lower cost without the common limitations and risks related to the microbial systems. Ethylenediamine (EDA) was used to extract the crude oil dissolved biosurfactants (as anionic surfactants) of a crude oil sample to the aqueous phase and form a cat-ionic surfactant complex. The biosurfactant was isolated from the crude oil and preliminarily characterized which was capable of reducing the surface tension to 48 mN/m. Various concentrations of EDA were utilized to extract the crude oil biosurfactants and their effectiveness on the oil recovery was studied in a glass micro-model. Results indicated that an incremental 22 % oil production was obtained by flooding the 10 mM EDA solution. The incremental oil production was related to the formation of the cat-ionic complex surfactant which believed to cause a significant IFT reduction and simultaneously, have a higher efficiency in the wettability alteration than the anionic biosurfactants. It can be concluded that the extraction of the indigenous biosurfactant content of the crude oil and their interaction by EDA can be considered as a low-cost low-risk potential to the enhanced oil recovery processes.

L-Phenylacetylcarbinol (L-PAC) which is used as a precursor for the production of ephedrine and pseudoephedrine is the first reported biologically produced α-hydroxy ketone compound. l-PAC is commercially produced by the yeast Saccharomyces cerevisiae. Yeast cells transform exogenously added benzaldehyde into l-PAC by using the action of pyruvate decarboxylase (PDC) enzyme. In this work, genome-scale model and flux balance analysis were used to identify novel target genes for the enhancement of l-PAC production in yeast. The effect of gene deletions on the flux distributions in the metabolic model of S. cerevisiae was assessed using OptGene and minimization of metabolic adjustments. Six single gene deletion strains, namely Δrpe1, Δpda1, Δadh3, Δadh1, Δzwf1 and Δpdc1, were predicted in silico and further tested in vivo by using knock-out strains cultivated semi-anaerobically on glucose and benzaldehyde as substrates. Δzwf1 mutant exhibited the highest l-PAC formation (2.48 g/L) by using 2 g/L of benzaldehyde which is equivalent to 88 % of the theoretical yield.

The enzymatic production of formate from CO2 with the immobilized NADH-dependent formate dehydrogenase (FDH) on the activated electrospun polystyrene nanofibers (EPSNF) was investigated to develop a sustainable process for CO2 reduction. Direct electrochemical regeneration on a Cu foam electrode was employed to supply the reaction with the reduced cofactor (NADH). The formate production was studied in two modes of batch and semi-continuous operations with the cofactor recycle. Results indicated that the regenerated cofactor concentrations in both systems were nearly identical (0.5 mM) which ensured the desirable activity of the immobilized enzyme. This showed that the electrochemical regeneration system was effective even in the semi-continuous operation. Although the cumulative formate concentration in the batch operation was higher, the total amounts of the produced formate were higher for the semi-continuous mode for more than 42% which was justified by the fact that the lower formate concentration in the semi-continuous mode would be favorable to the progress of the enzymatic CO2 to formate conversion. Finally, it was concluded that the proposed semi-continuous process in this work could be considered as a promising process for the enzymatic CO2 conversion.

The capability of oxalic acid produced by Aspergillus niger was investigated for bioleaching of platinum from a refinery reforming catalyst. The spent medium mode was selected for bioleaching because of its higher efficiency at favorable pH and temperature conditions. The effects of several important factors such as the pulp density, pH and temperature on platinum recovery were optimized using Box-Behnken design of response surface methodology. The results indicated that pH adjustment during the bioleaching process increases the final platinum recovery significantly. The obtained optimum conditions were 1% for the pulp density, 0.5 for the medium pH, and 70 degrees C for the temperature which led to 37% platinum recovery. The significance of oxalic acid as the leaching agent in platinum bioleaching was highlighted by investigating the recovery of a blank medium without oxalic acid at the optimum conditions which was just about 13%. The presented method can be utilized in an environmentally friendly process to recover platinum from industrial catalysts. (C) 2019 Elsevier Ltd. All rights reserved.

Two species of microalgae (Chlorella vulgaris and Dunaliella tertiolecta) as the biological agents along with ZnO nanoparticles as the photocatalyst were used to investigate the hydrocarbon removal efficiency from oily water samples. Firstly, the toxicities of the photocatalyst, normal paraffine hydrocarbons and their combination towards the microalgae were evaluated in terms of cell growth and chlorophyll content. The capability of algae to absorb the nanoparticles in the aqueous phase was confirmed by FT-IR spectroscopy. Then, the hydrocarbon removal efficiencies of the algae, photocatalyst and the combined photocatalyst-algae system were studied by measuring the residual hydrocarbon content of the samples. Results indicated that despite of the growth inhibitory effects of n-alkanes and nanoparticles on the examined algae, both of them could survive in the system. Dunaliella tertiolecta was more affected by normal paraffins while Chlorella vulgaris was more sensitive to ZnO nanoparticles. Both of the studied species were capable of hydrocarbon removal and the efficiency of Chlorella vulgaris was superior. The combination of algae and nanoparticles was also proved to have a synergistic effect on degradation of the hydrocarbon content of the medium. The obtained removal efficiencies for initial hydrocarbon concentrations of 0.05%, 0.1% and 0.5% (v/v) were 100%, 78% and 42% for Dunaliella tertiolecta-ZnO and 100%, 93% and 88% for Chlorella vulgaris- ZnO system, respectively. It can be concluded that the examined microalgae-nanoparticle system can be considered as a final polishing step in hydrocarbons removal from oily waters.

Purpose: Glucose decorated PLGA and chitosan nanoparticles (GPNPs and GCNPs) have been developed to examine the possibility of preventing the facilitated glucose transport to the cells through blocking the glucose transporters (Gluts) overexpressed by tumor cells. Methods: The MTT assay was used to assess the cytotoxicity towards human colon tumor (HT-29) cells in 72 hrs. Fluorescence microscopy was employed to confirm the attachment of GPNPs to the cells. Moreover, the GPNPs effects on the apoptotic rate of HT-29 cells were analyzed. Finally, the expression levels of GLUT-1 and GLUT-4 by real-time polymerase chain reaction (RT-PCR) were assayed to investigate the response of HT-29 cells to blocking their Gluts by GPNPs. Results: The stability studies showed that the synthesized complexes were mostly stable (more than 80%) at various temperatures (4 to 40 degrees C) and pH (5.4 to 7.4) conditions. Results indicated that the survival rate of the cells was decreased to 43% and 46% after treatment with GCNPs and GPNPs, respectively. Also, the apoptosis assay results showed that the percentage of viable cells reduced to 47% after GPNPs treatment. These observations were justified by the specific interactions between the glucose terminals and the cells Gluts which resulted in blocking the entries of nutrients to the cells. It was revealed that the GLUT-1 mRNA expression after the first 24 h of treatment by GPNPs was upregulated to more than 145%, while the direction was reversed after 72 h (expression less than 45%), which coincided with the cells death. In the first 24 h, the glucose deprivation stimulated the expression of Glut-1 while the apoptotic enzymes expression was dominant at the end of 72 h treatment time. Conclusion: Finally, it can be concluded that the glucose-nanoparticle complexes could be considered as promising agents in cancer therapy.

Blending polyolefins with certain types of natural polymers like starch can be beneficial to their biodegradation. The impact of alpha-amylase on the biodegradation of low-density polyethylene (LDPE)-starch blend samples in an aqueous solution was investigated through characterizing their physical, mechanical and chemical properties. Results indicated that the weight and tensile strength of the enzyme treated samples were reduced by 48% and 87% respectively. Moreover, differential scanning calorimetry (DSC) showed an increase in fusion enthalpy of degraded samples which means that the crystallinity has been increased. The biodegradation of LLDPE appeared in Fourier-transform infrared spectroscopy (FT-IR) through the reduction in the intensity of the related peaks. This observation was supported by energy dispersive x-ray spectroscopy (EDXS) analysis where decreasing the percentage of carbon atoms in the treated blend was obtained. Likewise, the gel permeation chromatography (GPC) results pointed to a significant reduction in both the molecular weight and viscosity of LDPE more than 70% and 60% respectively. Furthermore, thermal gravimetric analysis (TGA) affirmed the function of amylase in degradation of the blend. On the basis of the obtained results, it can be claimed that the main backbone of the polymer, as well as the side branches, have been scissored by the enzyme activity. In other words, alpha-amylase has a promiscuous cometabolic effect on biodegradation of LDPE in polymer-starch blends.

Enzymatic conversion of CO2 to formate was carried out in the cathodic cell of a two-chamber electrochemical apparatus where NAD(+) was reduced on the surface of a Copper foam electrode. Formate dehydrogenase (FDH) was used as the biocatalyst in both free form and immobilized on the modified electrospun polystyrene nanofibers (EPSNF). The fabricated EPSNF were modified by a multistage procedure including acid treatment, silanization followed by activation with glutaraldehyde. The effects of regenerated NADH concentration and time of enzymatic reaction on the formate production in the both systems were studied. The results indicated that the EPSNF immobilized FDH had a desirable activity, long-term storage stability (41% after 20 days) and reusability after eight cycles of successive reactions (53% of the initial activity). Moreover, it was revealed that the increase of cofactor concentration at the early times of reaction was favorable to the formate production. However, an inhibitory effect was observed at higher concentrations of NADH, and the optimum values of 0.45mM and 0.51mM were obtained for the maximum enzyme activity by the free and immobilized enzymes respectively. The produced formate at the optimum cofactor concentration after 300 min was 0.61mM and 0.31mM for the free and immobilized enzyme systems. Finally, it can be concluded that the presented process is a promising approach to the enzymatic conversion of CO2.

This study investigated different methodsof controlling the fat, oil and grease (FOG) in sewer systems. A comprehensive control program wasdevelopedfor the city of Mashhad (Iran) to maintain its sewer system and prevent blockages. The control program consisted of three parts: 1) fat, oil and grease source control, 2) sewer system modification and 3) preventive maintenance. This program includedguidelinesfor food service establishments, which are the majorsources of (FOG). Food service establishments must implementbetter management practices to reduce (FOG)from entering the facility drain and install grease removal devices.As a part of preventive cleaning, theperformance of several surfactants was evaluated as a cleaning agent. A 50:50 mixture (10 v. % in water) of two industrial surfactants, one containing monoethyl amine and sulfonated lauryl alcohol and one containing nonylphenolethoxylate and potassium hydroxide,had the best performance and removed 80 % of the fat. Response Surface Methodology was used to determine the optimum conditions for the surfactant.The optimum conditions were acontact time of 36 h, shaking rate of 30 rpm andsurfactant concentration of 12.5%.The second part of the program consisted ofremoving dead zones and increasing wastewater velocity in the sewer lines to enhance thehydraulic condition of thesewer system and decrease fat deposition.Finally, a detailed and well-defined control program couldsolve FOG problems in sewer systems.

Improvement of alkaline protease production, one of the most important types of industrial biocatalysts, is essential for commercial purposes. The present study’s aim was to increase alkaline protease production of MSB42, a newly isolated strain of Exiguobacterium sp., through the rotatable central composite design (RCCD). In this regard, parameters affecting MSB42 enzyme production were chosen based on the results of preliminary one-factor-at-a-time (OFAT) experiments. According to the results of RCCD, the enzyme production showed its maximum level (198.48 U/ml) in the presence of 3% w/v glucose, 3% w/v peptone, at 37 °C and pH 9. Overall, the enzyme production was 2 and 3.24 times more than OFAT experiments (98.69 U/ml) and unoptimized conditions (61.29 U/ml), respectively. A polynomial model of MSB42 alkaline protease production was obtained using the experimental date and based on the significant terms. The protease gene of this strain was also amplified using the designed primers (873 bp), and based on the sequencing results, was found to be closely related to the M6 family of metalloprotease domain.

Biodemulsifier production by Acinetobacter calcoaceticus and its capability to break the stable water in oil emulsions were investigated. The chemical structure of the isolated biodemulsifiers from cultivation on various nitrogen sources were preliminarily analyzed by Fourier-transform infrared spectroscopy (FT-IR). The cultivation conditions such as temperature, pH and carbon to nitrogen source concentration (C/N) ratio were optimized for maximum demulsification activity through response surface methodology. It was disclosed that the composition of the isolated biodemulsifiers was depended on the utilized nitrogen source in the medium and altered from a cyclic lipopeptide (on soybean) to a lipopolysaccharide (on ammonium salts). The obtained optimum conditions for the biodemulsifier produced on ammonium nitrate (as the nitrogen source) were 35 degrees C for temperature, 10 for C/N ratio and 5 for pH. Results indicated that the produced extracellular biodemulsifier can reduce the surface tension to 38.6 mN/m and break 95% of a surfactant stabilized emulsion at the optimum conditions.