Exploring the potential of a novel alternating current stimulated iron‑carbon anammox process: A new horizon for nitrogen removal

This study explored a novel alternating current (AC) stimulation approach to enhance the nitrogen removal efficiency of an iron‑carbon based anammox (FeC anammox) system. In the preliminary experiment, the TN removal efficiency of the AC stimulated system was 8.06 % higher than that of a DC simulated system in same current densities of 0.25 mA/cm2. Gene expression analysis revealed that the AC-stimulated system, where, compared with the anammox system alone, the expression of HZS, HDH, NarG, NirS, NorB and NosZ increased by 1.81, 2.50, 1.64, 0.23, 1.15 and 1.27 times, respectively. In the continuous experiment, the TN removal rate increased from 60.13 % to 84.34 % after AC stimulation, and the working time of the FeC materials increased to 20 days. An analysis of the mechanism revealed that the parallel connection between the capacitive reactance and filler resistance in AC might reduce the internal resistance of the system, thereby improving the actual current density received by local microorganisms, and achieving a better strengthening effect.

Molecular Biology Applications of Psychrophilic Enzymes: Adaptations, Advantages, Expression, and Prospective

Psychrophilic enzymes are primarily produced by microorganisms from extremely low-temperature environments which are known as psychrophiles. Their high efficiency at low temperatures and easy heat inactivation property have attracted extensive attention from various food and industrial bioprocesses. However, the application of these enzymes in molecular biology is still limited. In a previous review, the applications of psychrophilic enzymes in industries such as the detergent additives, the food additives, the bioremediation, and the pharmaceutical medicine, and cosmetics have been discussed. In this review, we discuss the main cold adaptation characteristics of psychrophiles and psychrophilic enzymes, as well as the relevant information on different psychrophilic enzymes in molecular biology. We summarize the mining and screening methods of psychrophilic enzymes. We finally recap the expression of psychrophilic enzymes. We aim to provide a reference process for the exploration and expression of new generation of psychrophilic enzymes.

Expression of His-tagged NADPH-dependent acetoacetyl-CoA reductase in recombinant Escherichia coli BL-21(DE3)

Poly-3-hydroxybutyrate (P(3HB)), a member of the polyhydroxyalkanoate (PHA) family, is a biodegradable polyester with diverse industrial applications. NADPH-dependent acetoacetyl-CoA reductase (phaB) is the enzyme which plays an essential role in P(3HB) synthesis by catalyzing the conversion of the intermediates. The expression of phaB enzyme using the recombinant Escherichia coli BL-21(DE3) and the purification of the synthesized enzyme were studied. The pET-B3 plasmid harbouring the phaB gene derived from Ralstonia eutropha H16, was driven by the lac promoter in E. coli BL-21(DE3). The enzyme was expressed with different induction time, temperatures and cell age. Results showed that the cell age of 4 h, induction time of 12 h at 37°C were identified as the optimal conditions for the enzyme reductase expression. A specific activity of 0.151 U mg-1 protein and total protein concentration of 0.518 mg mg-1 of dry cell weight (DCW) were attained. Affinity chromatography was performed to purify the His-tagged phaB enzyme, in which enhanced the specific activity (14.44 U mg-1) and purification fold (38-fold), despite relative low yield (44.6%) of the enzyme was obtained. The purified phaB showed an optimal enzyme activity at 30°C and pH 8.0. The findings provide an alternative for the synthesis of the reductase enzyme which can be used in the industrial-scale production of the biodegradable polymers.

Finding and engineering the newly found bacterial superoxide dismutase enzyme to increase its thermostability and decrease the immunogenicity: a computational and experimental research

Superoxide dismutase (SOD) is one of the most important antioxidant enzymes that can reduce oxidative stress in the cell environment. Nowadays, bacterial sources of enzyme are commercially applicable in the cosmetics and pharmaceutical industries, but the allergenic effect of proteins from non-human sources has been mentioned as disadvantage of these kinds of enzymes. In this study, to find the suitable bacterial SOD candidate for decreasing immunogenicity, the sequences of five thermophilic bacteria were selected as reference species. Then, linear and conformational B-cell epitopes of the SOD were analyzed by different servers. The stability and immunogenicity of mutant positions were also evaluated. The mutant gene was inserted into the pET-23a expression vector and transformed into E. Coli BL21 (DE3) for expression of the recombinant enzyme. Afterward, the expression of the mutant enzyme was evaluated by SDS-PAGE analysis and the recombinant enzyme activity was assessed. Anoxybacillus gonensis was selected as a reasonable SOD source according to BLAST search, physicochemical properties analysis, and prediction of allergenic features. Regarding our results, five residues including E84, E142, K144, G147, and M148 were predicted as candidates for mutagenesis. Finally, the K144A was chosen as the final modification due to the increase in the stability of the enzyme and decreased immunogenicity of the enzyme as well. The enzyme activity was 240 U/ml at room temperature. Alternation in K144 to alanine caused increased stability of the enzyme. In silico studies confirmed non-antigenic protein after mutation.

Mechanistic insights into polyhydroxyalkanoate-enhanced denitrification capacity of microbial community: Evolution of community structure and intracellular electron transfer of nitrogen metabolism

Denitrification is the key driving force of nitrogen cycle in surface water and plays an important role in eutrophication water remediation. Compared with some other common carbon sources, such as glucose and sodium acetate, polyhydroxyalkanoates (PHAs) were found to have the distinguished advantages in screening specific denitrifying bacteria of natural surface water bodies. In this study, the large ensembles of taxa were obtained from surface water samples and then sub-cultured with PHA or glucose as the sole carbon source. The microbial community that could be screened by PHA was identified, and the environmental functions of these bacteria were analyzed. At the genus level, the main communities regulated by PHA included Pseudomonas (56.30 %), Acinetobacter (27.75 %), Flavobacterium (10.19 %) and Comamonas (3.14 %), which all had good denitrification ability. The changes in carbon source, nitrogen source and biomass (expressed by DNA) were simultaneously monitored when culturing the model strain (P. stuzeri) with PHA or glucose. Compared with the glucose group, less PHA was consumed to remove the same amount of nitrate within a shorter incubation time, and there was no significant difference in bacterial growth with PHA or glucose as the carbon source (glucose:ΔN:ΔC:ΔDNA = 1:18:0.072; PHA:ΔN:ΔC:ΔDNA = 1:11:0.063). PHA improved the denitrification efficiency by increasing the expression of NarGHI, NirB, NirK and NorB, i.e., the key enzymes in the denitrification process. In addition, PHA accelerated the assimilating rate of extracellular nitrate by bacteria through increasing the expression of NarK. Finally, PHA-regulated electron transfer during denitrification was studied by observing the changes in NADH and NAD⁺. PHA could use a large proportion of NADH to offer electrons for denitrification, which increased the rate of denitrification. Improved mechanistic insights into the PHA-enhanced denitrification capacity of the microbial community can provide novel options for the in-situ remediation of eutrophic surface water.

PHA stimulated denitrification through regulation of preferential cofactor provision and intracellular carbon metabolism at different dissolved oxygen levels by Pseudomonas stutzeri

Denitrification, a typical biological process mediated by complex environmental factors, i.e., carbon sources and dissolved oxygen (DO), has attracted great attention due to its contribution to the control of eutrophication and the biochemical cycling of nitrogen. However, the effects of carbon source on electron distribution and enzyme expression for enhanced denitrification under competition of electron acceptors (DO and nitrate) remain unclear. Here, we profile the carbon metabolic pathway of polyhydroxybutyrate (PHB) and glucose (Glu) at high and low DO levels (50% and 10% saturated DO, respectively). It was found that PHB enhanced the growth of Pseudomonas stutzeri (model denitrifying bacterium) and improved the specific nitrogen removal rate (SNRR) at all DO levels. The functional proteins had a better affinity for the cofactor nicotinamide-adenine dinucleotide (NADH) than for nicotinamide adenine dinucleotide phosphate (NADPH); thus, more electrons were involved in nitrogen reduction and intracellular PHB production in the PHB groups than in the Glu groups. Furthermore, the expression difference of enzymes in glucose and PHB metabolism was demonstrated by metaproteomic and target protein analysis, implying that PHB-driven intracellular carbon accumulation could optimize the intracellular electron allocation and correspondingly promote nitrogen metabolism. Our work integrated the mechanisms of intracellular carbon metabolism with preferences for electron transfer pathways in denitrification, providing a new perspective on how the selective parameters regulated microbial functions involved in denitrification.

Two-Tiered Selection and Screening Strategy to Increase Functional Enzyme Production in E. coli

Development of recombinant enzymes as industrial biocatalysts or metabolic pathway elements requires soluble expression of active protein. Here we present a two-step strategy, combining a directed evolution selection with an enzyme activity screen, to increase the soluble production of enzymes in the cytoplasm of E. coli. The directed evolution component relies on the innate quality control of the twin-arginine translocation pathway coupled with antibiotic selection to isolate point mutations that promote intracellular solubility. A secondary screen is applied to ensure the solubility enhancement has not compromised enzyme activity. This strategy has been successfully applied to increase the soluble production of a fungal endocellulase by 30-fold in E. coli without change in enzyme specific activity through two rounds of directed evolution.

Exploitation of ammonia-inducible promoters for enzyme overexpression in Bacillus licheniformis

Ammonium hydroxide is conventionally used as an alkaline reagent and cost-effective nitrogen source in enzyme manufacturing processes. However, few ammonia-inducible enzyme expression systems have been described thus far. In this study, genomic-wide transcriptional changes in Bacillus licheniformis CBBD302 cultivated in media supplemented with ammonia were analyzed, resulting in identification of 1443 differently expressed genes, of which 859 genes were upregulated and 584 downregulated. Subsequently, the nucleotide sequences of ammonia-inducible promoters were analyzed and their functionally-mediated expression of amyL, encoding an α-amylase, was shown. TRNA_RS39005 (copA), TRNA_RS41250 (sacA), TRNA_RS23130 (pdpX), TRNA_RS42535 (ald), TRNA_RS31535 (plp), and TRNA_RS23240 (dfp) were selected out of the 859 upregulated genes and each showed higher transcription levels (FPKM values) in the presence of ammonia and glucose than that of the control. The promoters, P_copA from copA, P_sacA from sacA, P_pdpX from pdpX, P_ald from ald, and P_plp from plp, except P_dfp from dfp, were able to mediate amyL expression and were significantly induced by ammonia. The highest enzyme expression level was mediated by P_plp and represented 23% more α-amylase activity after induction by ammonia in a 5-L fermenter. In conclusion, B. licheniformis possesses glucose-independent ammonia-inducible promoters, which can be used to mediate enzyme expression and therefore enhance the enzyme yield in fermentations conventionally fed with ammonia for pH adjustment and nitrogen supply.

Comparison of three palm tree peroxidases expressed by Escherichia coli: Uniqueness of African oil palm peroxidase

Palm tree peroxidase has greater catalytic activity, stability and broad application prospects in comparison with horseradish peroxidase. However, slow growth, ecological destruction and high costs prohibit isolation of native peroxidases directly from palm trees. Bioreactor production of palm tree peroxidases would therefore be preferred to overcome such production limitations. Comparison of different recombinant glycan-free palm tree peroxidases would allow understanding the criticality of total glycans to the functions and characteristics. In the present study, African oil palm tree peroxidase expressed by Escherichia coli showed similar stability and 30-100-fold greater activity than that of recombinant royal palm tree peroxidases, but both of their comprehensive indexes were superior to the commercial, native horseradish peroxidase. Recombinant Chamaerops excelsa peroxidase showed no activity possibly due to incorrect protein folding. The results confirmed that recombinant expression by E. coli is potentially an effective means to obtain a mass of palm peroxidases with high activity and stability.

Heterologous expression of an active chitin synthase from Rhizopus oryzae

Chitin synthases are highly important enzymes in nature, where they synthesize structural components in species belonging to different eukaryotic kingdoms, including kingdom Fungi. Unfortunately, their structure and the molecular mechanism of synthesis of their microfibrilar product remain largely unknown, probably because no fungal active chitin synthases have been isolated, possibly due to their extreme hydrophobicity. In this study we have turned to the heterologous expression of the transcript from a small chitin synthase of Rhizopus oryzae (RO3G_00942, Chs1) in Escherichia coli. The enzyme was active, but accumulated mostly in inclusion bodies. High concentrations of arginine or urea solubilized the enzyme, but their dilution led to its denaturation and precipitation. Nevertheless, use of urea permitted the purification of small amounts of the enzyme. The properties of Chs1 (Km, optimum temperature and pH, effect of GlcNAc) were abnormal, probably because it lacks the hydrophobic transmembrane regions characteristic of chitin synthases. The product of the enzyme showed that, contrasting with chitin made by membrane-bound Chs's and chitosomes, was only partially in the form of short microfibrils of low crystallinity. This approach may lead to future developments to obtain active chitin synthases that permit understanding their molecular mechanism of activity, and microfibril assembly.

Ontogeny changes and weaning effects in gene expression patterns of digestive enzymes and regulatory digestive factors in spotted rose snapper (Lutjanus guttatus) larvae

The study of digestive physiology is an important issue in species that have been introduced in aquaculture like the spotted rose snapper (Lutjanus guttatus). The aims of this study were to describe the expression of digestive enzymes (trypsinogen, chymotrypsinogen, α-amylase, lipoprotein lipase, phospholipase A and pepsinogen) and their relation with orexigenic (neuropeptide Y, NPY) and anorexigenic (cholecystokinin, CCK) factors during the larval development and to evaluate the effect of weaning in their expression. The results showed that the transcripts of all the assayed digestive enzymes, with the exception of pepsinogen, and NPY and CCK were already present in L. guttatus from the hatching stage. The expression of all the enzymes was low during the yolk-sac stage (0-2 days after hatching, DAH), whereas after the onset of exogenous feeding at 2 DAH, their expression increased and fluctuated throughout larval development, which followed a similar pattern as in other marine fish species and reflected changes in different types of food items and the progressive maturation of the digestive system. On the other hand, weaning of L. guttatus larvae from live prey onto a microdiet between 25 and 35 DAH significantly affected the relative expression of most pancreatic digestive enzymes during the first weaning days, whereas chymotrypsinogen 2 and lipoprotein lipase remained stable during this period. At the end of co-feeding, larvae showed similar levels of gene expression regardless of the diet (live prey vs. microdiet), which indicated that larvae of L. guttatus were able to adapt their digestive capacities to the microdiet. In contrast, feeding L. guttatus larvae with live feed or microdiet did not affect the expression of CCK and NPY. The relevance of these findings with regard to current larval rearing procedures of L. guttatus is discussed.

Biodegradation and reversible inhibitory impact of sulfamethoxazole on the utilization of volatile fatty acids during anaerobic treatment of pharmaceutical industry wastewater

This study evaluated the chronic impact and biodegradability of sulfamethoxazole under anaerobic conditions. For this purpose, a lab-scale anaerobic sequencing batch reactor was operated in a sequence of different phases with gradually increasing sulfamethoxazole doses of 1 to 45 mg/L. Conventional parameters, such as COD, VFA, and methane generation, were monitored with corresponding antimicrobial concentrations in the reactor and the methanogenic activity of the sludge. The results revealed that anaerobic treatment was suitable for pharmaceutical industry wastewater with concentrations of up to 40 mg/L of sulfamethoxazole. Higher levels exerted toxic effects on the microbial community under anaerobic conditions, causing the inhibition of substrate/COD utilization and biogas generation and leading to a total collapse of the reactor. The adverse long-term impact was quite variable for fermentative bacteria and methanogenic achaea fractions of the microbial community based on changes inflicted on the composition of the residual organic substrate and mRNA expression of the key enzymes.

Implication of caspase-3 and granzyme B expression and activity in spleenocytes of ehrlich ascites carcinoma mice subjected to immunotherapy

Background

Caspase-3 and granzyme B were claimed as apoptotic manipulative enzymes.

Aims

The present study was to determine the enzymes expression and activity in cancer and cancer immune therapeutic status and the possible association to cancer common pathological signs targeting the improvement of therapeutic conditions.

Material and Methods

Mice were immunized with cell lyaste or cell lysate + CKI in the right thigh and challenged with live cells of ehrlich ascites carcinoma (EAC) in the left thigh. The expression and activity of both enzymes in the spleenocytes derived from different subjects (normal, EAC and cell lysate or cell lysate + CKI immunized mice) after cultured with EAC viable cells were determined by colorimetric assay and western blot analysis. In addition, the subjects DNA ladder and serum metalloproteases (MMP 2 and 9) zymography were observed.

Results

The experimental data revealed over expression of caspase3 and granzyme B in the groups of cell lysate or cell lysate + CKI immunized mice compared to control while down expression were recorded in the EAC subject. The over expression of the 2 enzymes were accompanied with increases in the activities of caspase3 and granzyme B, changes in DNA fragmentation and inhibition of metalloproteases.

Conclusion

It could be suggested that, the parameter estimation within the present experimental framework could identify the efficiency of therapeutic vaccine protocols and elucidate the impact of CKI adjuvant with vaccines therapy.