Purification and characterization of a serine protease secreted by Brevibacillus sp. KH3 for reducing waste activated sludge and biofilm formation

Stress response proteins within biofilm matrixome protect the cell membrane against heavy metals-induced oxidative damage in a marine bacterium Bacillus stercoris GST-03

Biofilm formation is a key adaptive response of marine bacteria towards stress conditions. The protective mechanisms of biofilm matrixome proteins against heavy metals (Pb and Cd) induced oxidative damage in the marine bacterium Bacillus stercoris GST-03 was investigated. Exposure to heavy metals resulted in significant changes in cell morphology, biofilm formation, and matrixome composition. Biofilm-encased cells showed lower oxidative damage. Biofilm matrixome protein exhibited major conformational changes, with 100 % α-helix turned to 62.33 % and 69.64 % of random coil under Pb and Cd stress, respectively. Fluorescence quenching kinetics revealed slow interactions between biofilm matrixome proteins and heavy metals (Kq values < 2.0 × 1010). Thermodynamic analysis showed negative ∆G (-16.02 kJ/mol for Pb and -17.45 kJ/mol for Cd) and binding dissociation constant (KD) (1530 ± 157 μM for Pb and 875 ± 97.4 μM for Cd), indicating a stronger binding affinity of biofilm matrixome to heavy metals. Pb stress led to overproduction of detoxification proteins (YnaI, KhtS, Bacillopeptidase F), competence and sporulation proteins (RapF, CSSF, XkdP), while Cd exposure leads to overproduction of proteins involved in protein misfolding repair (YlxX, cysteine-tRNA ligase, YacP), DNA repair (YfkN), and redox balance (cysteine synthase, YdiK). The findings highlight the resilience of B. stercoris GST-03 to heavy metal stress in biofilm mode.

Carboxylated nanocellulose from quinoa husk for enhanced protease immobilization and stability of protease in biotechnological applications

Herein, an efficient and feasible approach was developed to oxidize low-cost agricultural waste (quinoa husk, QS) for the synthesis of carboxylated nanocellulose (CNC). The as-prepared rod-like CNCs (average diameter of 10 nm and length of 103 nm) with a high specific surface area (173 m2/g) were utilized for the immobilization of a model protease enzyme (PersiProtease1) either physically or via covalent attachment. For chemical immobilization, CNCs were firstly functionalized with N, N'-dicyclohexylcarbodiimide (DCC) to provide DCNCs nanocarrier which could covalently bond to enzyme trough nucleophilic substitution reaction and formation of the amide bond between DCNCs and enzyme. The immobilization efficiency, activity, stability, kinetic parameters, and reusability of covalently attached and physically immobilized PersiProtease1 were similar to those of the free enzyme. Enzyme immobilization resulted in higher thermal stability of the enzyme at elevated temperatures (> 80 °C), and the covalently immobilized enzyme displayed higher reusability than its physically immobilized form (56% vs. 37% activity, after 15 consecutive cycles), which would be rooted in a more tightly attached and less leached enzyme in the case of PersiProtease1/DCNCs. This study demonstrates the significance of using agricultural by-products and the enhanced performance and stability of immobilized proteases.

Revolutionizing protein hydrolysis in wastewater: Innovative immobilization of metagenome-derived protease in periodic mesoporous organosilica with imidazolium framework

This research focused on utilizing periodic mesoporous organosilica with imidazolium framework (PMO-IL), to immobilize a metagenome-sourced protease (PersiProtease1), thereby enhancing its functional efficiency and catalytic effectiveness in processing primary proteins found in tannery wastewater. The successful immobilization of enzyme was confirmed through the use of N2 adsorption-desorption experiment, XRD, FTIR, TEM, FESEM, EDS and elemental analytical techniques. The immobilized enzyme exhibited greater stability in the presence of various metal ions and inhibitors compared to its free form. Furthermore, enzyme binding to PMO-IL nanoparticles (NPs) reduced leaching, evidenced by only 11.41 % of enzyme leakage following a 120-min incubation at 80 °C and 6.99 % after 240 min at 25 °C. Additionally, PersiPro@PMO-IL maintained impressive operational consistency, preserving 62.24 % of its activity over 20 cycles. It also demonstrated notable stability under saline conditions, with an increase of 1.5 times compared to the free enzyme in the presence of 5 M NaCl. The rate of collagen hydrolysis by the immobilized protease was 46.82 % after a 15-minute incubation at 60 °C and marginally decreased to 39.02 % after 20 cycles indicative of sustained efficacy without significant leaching throughout the cycles. These findings underscore the effectiveness of PMO-IL NPs as a viable candidate for treating wastewater containing protein.

The Performance and Mechanism of Sludge Reduction by the Bioaugmentation Approach

Simple Summary

Activated sludge-based wastewater treatment process is one of the most popular adopted systems in wastewater treatment plants around the world. Excess sludge is an inevitable byproduct of the process, and the enormous quantity has brought a significant burden on operational costs. Various physicochemical and biological methods have been developed. Biological-based methods are promising because of less chemical consumption and low operation cost comparing to physicochemical methods. Hence, the present study is aimed at searching for functional bacteria that could reduce sludge, enhance the performance of sludge reduction through optimization, and try to unveil the underlying mechanism during sludge reduction. A total of 19 strains that belong to Firmicutes, Proteobacteria, and Actinobacteria were successfully isolated and identified. Subsequently, the performance of sludge reduction by pure culture or mix-cultures was validated. In total, 21.2% and 13.9% of total suspended and volatile suspended solids were reduced within 48 h after optimization via response surface methodology. The three-dimensional excitation-emission matrix fluorescence spectrum and hydrolases test results revealed that the sludge reduction might be promoted by the strain mainly through hydrolysis via proteinase and amylase. The results obtained from the study could help us to find an effective and economical way to resolve the sludge issue.

Abstract

Millions of wastewater treatment plants (WWTPs) based on the activated sludge process have been established worldwide to help to purify wastewater. However, a vast amount of sludge is inevitably generated, and the cost of sludge disposal could reach over half of the total operation cost of a WWTP. Various sludge reduction techniques have been developed, including physicochemical, biological, and combinational methods. Micro-organisms that could reduce sludge by cryptic growth are vital to the biological approach. Currently, only limited functional bacteria have been isolated, and the lack of knowledge on the underlying mechanism hinders the technique development. Therefore, the present study is aimed at isolating sludge-reducing bacteria and optimizing the sludge reduction process through response surface methodology. Nineteen strains were obtained from sludge. The mix-cultures did not show a higher sludge reduction rate than the pure culture, which may be ascribed to the complicated interactions, such as competition and antagonistic effects. In total, 21.2% and 13.9% of total suspended and volatile suspended solids were reduced within 48 h after optimization. The three-dimensional excitation-emission matrix fluorescence spectrum and hydrolases test results revealed that the sludge reduction might be promoted by the strain mainly through hydrolysis via proteinase and amylase. The results obtained from the study demonstrate the potential of using micro-organisms for sludge reduction through cryptic growth.

Impact of 5-fluorouracil on anaerobic digestion using sewage sludge

The role of bacterial interaction is vital to control bacterial functions; however, it has not been fully understood in microbial consortia (including anaerobic digestion). In this study, fluorouracil (FU), which is an anticancer agent and a quorum sensing (QS) inhibitor to some of the Gram-negative bacteria was found to inhibit methane production from sewage sludge under anaerobic conditions, as shown in a result where methane production in the presence of FU was eight times lower than the control (sewage sludge without FU). Whereas FU did not influence the hydrolysis process, in the acidogenesis/acetogenesis process, butyrate, and acetate accumulated in samples with FU. Also, in the methanogenesis process, FU remarkably inhibited methane production by acetoclastic methanogens rather than by the hydrogenotrophic ones. This result agreed with the result that growth and methane production of Methanosarcina acetivorans C2A was inhibited in the presence of FU. However, the inhibitory effect of FU was high in the condition that both bacteria and archaea were active. It indicates that FU influences methanogens and bacteria in the process of methane fermentation. The analyses of microbial communities (bacteria and archaea) showed that the abundance ratio of the Firmicutes phyla is high, and hydrogenotrophic methanogens become dominant in the presence of FU. Conversely, the abundance of Spirochaetes significantly decreased under FU. The inhibition of methane production by FU was due to the growth inhibition of methanogenic archaea and the changes in the composition of the bacterial population.

A Newly Isolated Strain Lysobacter brunescens YQ20 and Its Performance on Wool Waste Biodegradation

Wool keratin is difficult to degrade as comparing to feathers because of its tough secondary structure. In order to develop an approach for high-value utilization of wool fiber waste by keratinolytic microorganisms, which is produced from shearing, weaving, and industrial processing of wool, screening of wool-degrading bacterium with high degradation efficiency were performed in this study. To this end, Lysobacter brunescens YQ20 was identified and characterized. The optimized conditions for wool degradation were pH 9.0 and 37°C with 20% liquid volume of Erlenmeyer flask. After fermentation, 15 essential amino acids were detected when wool fiber waste was fermented. The total amino acids produced from 1% wool per hour were 13.7 mg/L. The concentration was 8.6-fold higher than that produced by the strain Stenotrophomonas maltophilia BBE11-1, which had previously been reported to have the highest wool-degrading capacity. Our study reports the first Lysobacter strain that exhibits efficient wool degradation and yields higher concentrations of amino acids than previously reported strains. Whole-genome sequencing indicated that there were 18 keratinase-like genes in the genome of YQ20, which exhibited a long evolutionary distance from those of Bacillus. Therefore, L. brunescens YQ20 may have applications in the environmentally friendly management of wool waste as fertilizer in agriculture.

Simultaneous hydrolysis of various protein-rich industrial wastes by a naturally evolved protease from tannery wastewater microbiota

Elimination of protein-rich waste materials is one of the vital environmental protection requirements. Using of non-naturally occurring chemicals for their remediation properties can potentially induce new pollutants. Therefore, enzymes encoded in the genomes of microorganisms evolved in the same environment can be considered suitable alternatives to chemicals. Identification of efficient proteases that can hydrolyze recalcitrant, protein-rich wastes produced by various industrial processes has been widely welcomed as an eco-friendly waste management strategy. In this direction, we attempted to screen a thermo-halo-alkali-stable metagenome-derived protease (PersiProtease1) from tannery wastewater. The PersiProtease1 exhibited high pH stability over a wide range and at 1 h in pH 11.0 maintained 87.59% activity. The enzyme possessed high thermal stability while retaining 76.64% activity after 1 h at 90 °C. Moreover, 65.34% of the initial activity of the enzyme remained in the presence of 6 M NaCl, showing tolerance against high salinity. The presence of various metal ions, inhibitors, and organic solvents did not remarkably inhibit the activity of the discovered protease. The PersiProtease1 was extracted from the tannery wastewater microbiota and efficiently applied for biodegradation of real sample tannery wastewater protein, chicken feathers, whey protein, dehairing sheepskins, and waste X-ray films. PersiProtease1 proved its enormous potential in simultaneous biodegradation of solid and liquid protein-rich industrial wastes based on the results.

Enhanced sludge reduction during swine wastewater treatment by the dominant sludge-degrading strains Chryseobacterium sp. B4 and Serratia sp. H1

Sludge reduction is considered a main target for sludge treatment and an urgent issue for wastewater treatment. In this study, two dominant sludge-degrading strains, identified as Chryseobacterium sp. B4 and Serratia sp. H1, were used for inoculation in swine wastewater treatment to investigate the enhancement of sludge reduction. The results showed the volatile suspended solid (VSS) removal rate in experimental groups inoculated with Chryseobacterium sp. B4, Serratia sp. H1, and a combination of the two strains improved by 49.4%, 11.0%, and 30.5%, compared with the control with no inoculation. Furthermore, microbial community structure and functional prediction analyses indicated Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria could play an essential role in sludge reduction, and the dominant sludge-degrading strains B4 and H1 enhanced sludge reduction by strengthening carbohydrate, nucleotide, amino acid, and lipid metabolism and membrane transport functions. This study provides new insights into sludge reduction during wastewater treatment with dominant sludge-degrading strains.

Diluted Luria-Bertani medium vs. sewage sludge as growth media: comparison of community structure and diversity in the culturable bacteria

Because colony formation is essential to seek bacterial functions by the direct observation of phenotype, the diversification of colony formation for culturable bacteria is a big challenge in the research field of Environmental Biotechnology. In this study, the biodiversity of cultivable bacteria (colony or liquid culture) was compared by using Luria-Bertani (LB) medium and waste sewage sludge (WSS) under different dilutions and temperatures. When WSS was used as a bacterial source, whereas the highest number of colonies was found at the concentration of WSS (5%), a particular concentration of LB (10%) or WSS (1%) as a growth medium showed the best number of the operational taxonomic units (OTUs) of colonies. The results of bacterial community structure indicated that there are 1, 8, and 12 bacterial genera found uniquely in the agar plates of LB, 10% LB, and 5% WSS. By contrast, when palm oil mill effluent sludge was used as a bacterial source, the effect of dilution was different with WSS. When comparing the biodiversity between colonies and liquid culture, a high OTU value was observed in the colonies on the plate. In addition, 30°C showed the highest number of colonies in LB, 10% LB, and 5% WSS whereas the best OTUs were observed at 37°C for LB and 10% LB, and at 25°C for 5% WSS. This study demonstrates the diversification of cultivable bacteria through the number of OTUs in diluted LB medium and WSS, which is beneficial to isolate a unique bacterial strain.Key points• Impacts of diluted LB medium and WSS for colony formation were determined.• Difference of concentration of LB and WSS made different effects on colony formation.• Temperature change affected on diluted LB and WSS as media.

Enrichment of waste sewage sludge for enhancing methane production from cellulose

Low ability of waste sewage sludge to degrade cellulose is observed due to its less cellulolytic bacteria content. The enrichment of sewage sludge in the absence or presence of carboxymethylcellulose (CMC) was conducted to improve anaerobic digestion (AD) of cellulose in this study. Compared to initial sewage sludge (IS), enriched sludge without CMC addition (ES) displayed 69.81% higher CH₄ yield and about 1.7-fold greater anaerobic biodegradation of cellulose. In particular, bacterial and archaeal diversities in samples inoculated with ES were significantly altered, with Ruminiclostridium and Methanobacterium as the predominant genera. Enriched sludge with CMC addition (ESC) displayed enhanced methane production at initial cellulose fermentation but showed no distinct difference compared with the control after incubation 24 days. These findings suggest that enrichment of waste sewage sludge without CMC addition is more beneficial for promoting AD of cellulose, providing a novel insight for efficient energy utilization of lignocellulosic wastes.

Changes in aerobic fermentation and microbial community structure in food waste derived from different dietary regimes

This study aimed to analyze the relationship between food components and food waste aerobic fermentation efficiency. Different food wastes were designed to be reflective of different dietary regimes, including formulated (R1), high oil/fat and salt (R2), high oil/fat and sugar (R3), and vegetarian (R4) diets, after which the physicochemical properties, enzyme activity, and structural characteristics of food waste microbial communities were examined to explore the potential mechanisms of food waste degradation under different dietary regimes. The main results of this study demonstrated that the physicochemical properties and hydrolase activity of different food waste were significantly different. The species richness in R2 and R3 food waste was higher than that of R1 and R4, whereas the community diversity of R1 and R4 food waste was higher than that of R2 and R3. At the genus level, the dominant bacteria in the four food waste types were Bacillus, Thermoactinomyces, Paenibacillus, and Cohnella.

Effect of Aso limonite on anaerobic digestion of waste sewage sludge

The effect of Aso volcanic limonite was explored in anaerobic digestion using waste sewage sludge (WSS). In this study, methane and hydrogen sulfide were remarkably inhibited when Aso limonite was mixed with WSS as well as a significant reduction of ammonia. Although pH was lowered after adding Aso limonite, methane was still inhibited in neutralized pH condition at 7.0. Hydrolysis stage was not influenced by Aso limonite as supported by the result that a high protease activity was still detected in the presence of the material. However, acidogenesis stage was affected by Aso limonite as indicated by the different productions of organic acids. Acetic acid, was accumulated in the presence of Aso limonite due to the inhibition of methane production, except in the highest concentration of Aso limonite which the production of acetate may be inhibited. Besides, the production of propionate and butyrate reduced in accordance to the increased concentration of Aso limonite. In addition, Archaeal activity (methanogens) in WSS with Aso limonite was low in agreement with the low methane production. Thus, these results indicate that Aso limonite influences the acidogenesis and methanogenesis processes, by which the productions of methane and ammonia were inhibited. On the other hand, in the contactless of Aso limonite during the anaerobic digestion of WSS (Aso limonite was placed in the area of headspace in the vial), Aso limonite had the adsorptive ability for hydrogen sulfide from WSS, but not for methane. This contactless system of Aso limonite may be a practical means to remove hydrogen sulfide without inhibiting methane production as an important bioenergy source.

Biosurfactants of Lactobacillus helveticus for biodiversity inhibit the biofilm formation of Staphylococcus aureus and cell invasion

Aim: This study aimed to evaluate the differences of biosurfactants produced by two Lactobacillus helveticus strains against the biofilm formation of Staphylococcus aureus in vitro and in vivo. Materials & methods: Scanning electron microscopy, Real time-quantitative PCR (RT-qPCR) and cell assay were used to analyze the inhibiting effect of biosurfactants against biofilm formation. Results & conclusion: Results showed that the biosurfactants have anti-adhesive and inhibiting effects on biofilm formation in vivo and in vitro. The biofilm-formative genes and autoinducer-2 signaling regulated these characteristics, and the biosurfactant L. helveticus 27170 is better than that of 27058. Host cell adhesion and invasion results indicated that the biosurfactants L. helveticus prevented the S. aureus invading the host cell, which may be a new strategy to eliminate biofilms.

Chitin extraction from shrimp waste by liquid fermentation using an alkaline protease-producing strain, Brevibacillus parabrevis

In this study, an extracellular protease, but no chitinolytic enzyme-producing strain, Brevibacillus parabrevis TKU046, has been isolated and analyzed for the deproteinization testing of shrimp waste by liquid fermentation. Deproteinization assays of shrimp waste with this microbe showed 95% protein removal after 4 days fermentation. The efficiency of chitin extraction by B. parabrevis TKU046 on wastes of three shrimp species were also investigated in which the highest deproteinization was found on cooked tiger shrimp shell. Infrared spectra (IR) of the obtained chitin displayed characteristic profiles for chitin. The culture supernatant released after fermentation greatly exhibited growth enhancing effect on Lactobacillus rhamnosus. In addition, B. parabrevis TKU046 protease was isolated and determined the characteristics. The molecular mass of B. parabrevis TKU046 protease was determined as 32 kDa and 34 kDa, respectively, by SDS-PAGE and HPLC. Overall, the findings provide strong support for the potential candidacy of this enzyme as an effective and eco-friendly alternative to the conventional chemicals used for the deproteinization of shrimp heads in the chitin processing industry, as well as the production of prebiotics to be used in the nutraceutical industry.

Quorum sensing between Gram-negative bacteria responsible for methane production in a complex waste sewage sludge consortium

Quorum sensing (QS) plays a key role in activating bacterial functions through small molecules called autoinducers. In this study, the QS of Gram-negative bacteria in waste sewage sludge (WSS) was downregulated by adding the quorum quenching enzyme, AiiM lactonase, which cleaved the acyl-homoserine lactone (AHL) autoinducer signals from Gram-negative bacteria, and subsequently methane production was inhibited by over 400%. The pH was lowered after 2 days in the anaerobic fermentation whereas protease activity at the hydrolysis step was almost the same with or without AiiM. The production of acetic acid significantly increased during the fermentation in the presence of AiiM. The bacterial community at day 2 indicated that the population of Gram-positive bacteria increased in the presence of AiiM, and the percentage of Gram-negative bacteria decreased in the WSS containing AiiM. The change in the bacterial community in the presence of AiiM may be due to the different antimicrobial agents produced in the WSS because some of the Gram-positive bacteria were killed by adding the solid-phase extraction (SPE) fraction from the WSS without AiiM. In contrast, the SPE fraction with AiiM had reduced bactericidal activity against Gram-negative bacteria. Thus, bacterial signaling between Gram-negative bacteria is critical for methane production by the microbial consortia.

Effects of oxygen and water content on microbial distribution in the polyurethane foam cubes of a biofilter for SO2 removal

The performance of a biofilter for off-gas treatment relies on the activity of microorganisms and adequate O₂ and H₂O. In present study, a microelectrode was applied to analyze O₂ in polyurethane foam cubes (PUFCs) packed in a biofilter for SO₂ removal. The O₂ distribution varied with the density and water-containing rate (WCR) of PUFCs. The O₂ concentration dropped sharply from 10.2 to 0.8mg/L from the surface to the center of a PUFC with 97.20% of WCR. The PUFCs with high WCR presented aerobic-anoxic-aerobic areas. Three-dimensional simulated images demonstrated that the structure of PUFCs with high WCR consisted of an aerobic "shell" and an anoxic "core", with high-density PUFCs featuring a larger anoxic area than low-density PUFCs. Moreover, the H₂O distribution in the PUFC was uneven and affected the O₂ concentration. Whereas aerobic bacteria were observed in the PUFC surface, facultative anaerobic microorganisms were found at the PUFC core, where the O₂ concentration was relatively low. O₂ and H₂O distributions differed in the PUFCs, and the distribution of microorganisms varied accordingly.

Microbial Keratinases: Enzymes with Promising Biotechnological Applications

Keratin is a complex and structurally stable protein found in human and animal hard tissues, such as feathers, wool, hair, hoof and nails. Some of these, like feathers and wool, represent one of the main sources of protein-rich waste with significant potential to be transformed into value-added products such as feed, fertilizers or bioenergy. A major limitation impeding valorization of keratinous substrates is their recalcitrant structure and resistance to hydrolysis by common proteases. However, specialized keratinolytic enzymes produced by some microorganisms can efficiently degrade these substrates. Keratinases have already found a purpose in pharmaceutical, textile and leather industries. However, their wider implementation in other processes, such as cost-effective (pre)treatment of poultry waste, still requires optimization of production and performance of the available enzymes. Here we present a comprehensive review covering molecular properties and characteristics of keratinases, their classification, traditional and novel approaches in discovery of novel enzymes, production, characterization, improvement and biotechnological applications.

Microbial communities, extracellular proteomics and polysaccharides: A comparative investigation on biofilm and suspended sludge

Biofilm and suspended sludge (S-sludge) floc exhibit distinct physicochemical properties and process performances in an integrated fixed-film and suspended growth sequencing batch reactor. However, the mechanisms of governing these differences between the two aggregates were unknown. Current work evaluated the diversity of morphologies, microbial communities, extracellular proteins and polysaccharides between the biofilm and S-sludge. Contrast to biofilm, the denitrification was much more extensive performed in S-sludge. Furthermore, many microbial cells in the biofilm acted as the backbone of aggregates and maintained the structure stability. An extracellular protein observed only in the biofilm can promote the cell adhesion. In contrast, more extracellular proteins related to catalytic activity in the S-sludge could decrease the compactness of floc. In addition, the monosaccharide compositions from the two aggregates were various. These results could elucidate how the diversities of architecture and biochemical process between the two aggregates occurred.

Enhanced reduction of waste activated sludge at a low temperature by locally isolated strains Pseudomonas sp. VNT and Aeromonas sp. VNT

Appropriate control of waste activated sludge (WAS) is required to solve the annual increment of WAS volume. The low bacterial activity at low temperatures poses a difficulty in reducing or utilizing WAS in cold weather regions and/or during the winter season. This study reveals a practical method to enhance sludge reduction at a low temperature using isolated strains of Pseudomonas and Aeromonas species. The effect of inoculating each strain into WAS was examined at different temperatures (4°C, 10°C, 12°C, 15°C, 20°C, and 30°C) and under an aerobic condition. Sludge reduction showed 2- to 8-fold improvement at the temperature range from 4°C to 15°C. Both strains are psychrophilic and can produce protease and lipase for sludge degradation even at low temperatures. Thus, biological WAS treatment at a psychrophilic temperature can be enhanced by inoculating these promising strains.

Enhancement of sludge reduction and methane production by removing extracellular polymeric substances from waste activated sludge

The management of waste activated sludge (WAS) recycling is a concern that affects the development of the future low-carbon society, particularly sludge reduction and biomass utilization. In this study, we investigated the effect of removing extracellular polymeric substances (EPS), which play important roles in the adhesion and flocculation of WAS, on increased sludge disintegration, thereby enhancing sludge reduction and methane production by anaerobic digestion. EPS removal from WAS by ethylenediaminetetraacetic acid (EDTA) significantly enhanced sludge reduction, i.e., 49 ± 5% compared with 27 ± 1% of the control at the end the digestion process. Methane production was also improved in WAS without EPS by 8881 ± 109 CH4 μmol g(-1) dry-weight of sludge. Microbial activity was determined by denaturing gradient gel electrophoresis and real-time polymerase chain reaction, which showed that the hydrolysis and acetogenesis stages were enhanced by pretreatment with 2% EDTA, with a larger methanogenic community and better methane production.

Purification and characterization of alkaline-thermostable protease enzyme from Pitaya (Hylocereus polyrhizus) waste: a potential low cost of the enzyme

The thermoalkaline protease enzyme from pitaya (Hylocereus polyrhizus) waste was purified by a factor of 221.2 with 71.3% recovery using ammonium sulphate precipitation, gel filtration, and cation exchange chromatography. Gel filtration chromatography together with sodium dodecyl sulphate gel electrophoresis (SDS-PAGE) revealed that the enzyme is monomeric with a molecular weight of 26.7 kDa. The apparent K_m and V_max of the protease were 2.8 mg/mL and 31.20 u/min, respectively. The optimum pH and temperature were 8.0 and 70°C. The enzyme was highly active and stable over a wide pH range (from pH 3.0 to pH 11.0 with the optimum activity at pH 8.0). The protease has broad specificity toward azocasein, casein, hemoglobin, and gelatine. Activity of the enzyme was inhibited by Fe²⁺ and Zn²⁺, while protease activity was increased in the presence of Ca²⁺ and Mg²⁺ and Cu²⁺ by factors of 125%, 110%, and 105%, respectively. The alkaline protease showed extreme stability toward surfactants and oxidizing agent. The purified protease exhibited extreme stability in the presence of organic solvents and inhibitors. In addition, the enzyme was relativity stable toward organic solvents and chelating agents, such as ethylenediaminetetraacetic acid (EDTA). The enzyme, derived from pitaya peel, possesses unique characteristics and could be used in various industrial and biotechnological applications.

Effect of azithromycin on enhancement of methane production from waste activated sludge

In the methane production from waste activated sludge (WAS), complex bacterial interactions in WAS have been known as a major contribution to methane production. Therefore, the influence of bacterial community changes toward methane production from WAS was investigated by an application of antibiotics as a simple means for it. In this study, azithromycin (Azm) as an antibiotic was mainly used to observe the effect on microbial changes that influence methane production from WAS. The results showed that at the end of fermentation, Azm enhanced methane production about twofold compared to control. Azm fostered the growth of acid-producing bacterial communities, which synthesized more precursors for methane formation. DGGE result showed that the hydrolysis as well as acetogenesis stage was improved by the dominant of B1, B2 and B3 strains, which are Clostridium species. In the presence of Azm, the total population of archaeal group was increased, resulting in higher methane productivity achievement.

Influence of pretreated activated sludge for electricity generation in microbial fuel cell application

Influence of different pretreated sludge for electricity generation in microbial fuel cells (MFCs) was investigated in this study. Pre-treatment has shown significant improvement in MFC electricity productivity especially from microwave treated sludge. Higher COD reduction in the MFC has been revealed from microwave treated sludge with 55% for total and 85% for soluble COD, respectively. Nonetheless, longer ozonation treatment did not give additional advantage compared to the raw sludge. On the other hand, samples from anodes were analyzed using the 16S rRNA gene-based pyrosequencing technique for microbial community analysis. There was substantial difference in community compositions among MFCs fed with different pretreated sludge. Bacteroidetes was the abundant bacterial phylum dominated in anodes of higher productivity MFCs. These results demonstrate that using waste sludge as the substrate in MFCs could achieve both sludge reduction and electricity generation, and proper pre-treatment of sludge could improve the overall process performance.

Biochemical characteristics of a fibrinolytic enzyme purified from a marine bacterium, Bacillus subtilis HQS-3

A fibrinolytic enzyme isolated from marine Bacillus subtilis HQS-3 was purified to electrophoretic homogeneity using ammonium sulphate precipitation, alkaline solution treatment, membrane concentration, dialysis, ion exchange, and gel filtration chromatography. SDS-PAGE and gel filtration chromatography showed that it was a monomeric protein with an apparent molecular weight of 26 kDa. The purified enzyme was active at pH 6.0-10.0 with an optimum pH of 8.0. It was stable at temperatures ranging from 25 to 37 °C, exhibiting maximum activity between 45 °C and 50 °C. The isoelectric point of the enzyme was 9.0-9.2, which was higher than those of other known fibrinolytic enzymes from Bacillus species. PMSF, EDTA, Cu(2+), Zn(2+), and Co(2+) inhibited the enzyme activity significantly. This enzyme did not cause hemolysis in vitro and preferred direct degradation of fibrin in the following order: α, β, and γ-γ chains. Thus, these results suggest that the marine-derived enzyme is a plasmin-like serine metalloprotease, which is distinct from other fibrinolytic enzymes from genus Bacillus.

The overexpression of the SAPB of Bacillus pumilus CBS and mutated sapB-L31I/T33S/N99Y alkaline proteases in Bacillus subtilis DB430: new attractive properties for the mutant enzyme

The sapB gene encoding for Bacillus pumilus CBS protease (SAPB) and the triple mutated sapB-L31I/T33S/N99Y gene were cloned and overexpressed in the protease-deficient Bacillus subtilis DB430 using an Escherichia coli-Bacillus shuttle vector pBSMuL2. The 34,625.13 and 34,675.11-Da enzymes were purified from the culture supernatant of B. subtilis expressing the wild-type and mutated genes, respectively. The purified proteases showed the same N-terminal sequences and biochemical properties of those expressed in E. coli. Further investigations demonstrated that, compared to wild-type and other proteases, SAPB-L31I/T33S/N99Y had the highest catalytic efficiency and the best degree of hydrolysis. The mutant enzyme was also noted to exhibit a number of newly explored properties that are highly valued in the marketplace, namely considerable stability to detergents, higher resistance towards organic solvents, and potent dehairing ability. Overall, the findings indicated that SAPB-L31I/T33S/N99Y is a promising candidate for future use in a wide range of industrial and commercial applications.