Significance of bio-treatment by acid washing for enlargement of arsenic desorption in indigenous arsenic-resistant bacteria from gold mine

Mining activities can lead to the generation of large quantities of heavy metal, specifically arsenic which is released from a gold mine, causing widespread contamination of the ecosystem. Removal of carcinogenic and toxic arsenic from wastewater is essential for the safety of water that may be used for irrigation or drinking. In this study, three different of indigenous arsenic resistant bacterial strains were isolated from gold mine environment, Bacillus thuringiensis strain WS3, Pseudomonas stutzeri strain WS9, and Micrococcus yunnanensis strain WS11. WS9, WS3, and WS11 reached stationary phase after eight, ten, and seven hours, respectively, at 37 °C when grown in LB with arsenic. Gram staining showed WS9 as gram-negative rods, WS3 as grampositive rods, and WS11 as gram-positive cocci. From the Silver nitrate test, WS3 and WS11 reduced As (V) to As (III) while WS9 oxidized As (III) to As (V). The desorption of arsenic using acid washing and parameters affecting the desorption of arsenic such as acid concentration, time, adsorbent dosage, and different volume of acid solution were investigated. The batch experiments were carried out using bacterial biomass cultured in LB with 2 mM arsenite (III) and 5 mM arsenate (V). Optimum conditions for desorption arsenic were determined, being 1 M acid concentration at 37 °C and 2 hours of contact with (50 mg) bacterial biomass in 100 ml acid solution. The removal of arsenite and arsenate increased after acid washing of bacterial biomass of the three strains. Consequently, desorption of arsenic using acid washing is essential for biomass regeneration

Identification and optimization of biosurfactant producing bacteria isolated from rag layer crude oil emulsion

Biosurfactants are surface active compounds that synthesized as secondary metabolite by wide range of bacteria and have characteristic in lowering surface and interfacial tension. This study aimed to isolate and identify biosurfactant producing bacteria from rag layer crude oil emulsion. Rag layer is considered as undesirable material as it is difficult to be separated because of the stable interaction between different components. Mineral salt medium supplemented with glucose and crude oil was used to screen the ability of isolates to produce biosurfactant. Five bacterial strains that successfully isolated from rag layer crude oil emulsion sample were screened for hydrocarbon degradation and biosurfactant production. Two isolates shown positive results in drop collapse test, surface tension measurement and emulsification index, namely P3b and P4. 16S rRNA analysis revealed P3b and P4 to be closely related to Enterobacter xiangfangensis while P4 was Shewanella chilikensis, respectively. Only isolate P3b was selected for further study. Enterobacter xiangfangensis SSP3b16 was found to grow optimally at 37°C, pH 7.0 and 10mM glucose. The highest reduction of surface tension was recorded when culture medium supplemented with 7 % (v/v) glucose and 2 g/L ammonium nitrate. From this study, the biosurfactant production by Enterobacter xiangfangensisSSP3b16 can potentially be exploited to enhance oil recovery as well as in solving the rag layer problem in oil industries

Isolation and characterization PHB producing bacteria from waste cooking oil using pomegranate molasses as carbon source

Polyhydroxyalkanoates (PHAs) are biopolymers which have similar characteristics with petrochemical plastic but a step better due to its biodegradable property. Polyhydroxybutyrate (PHB) producing bacteria from waste cooking oil (WCO) was isolated and characterized based on its morphological and biochemical properties. Only one strain was isolated from different samples of WCO collected from different restaurants. The isolated bacterium was related to Bacillus thuringensis LMA which was identified and characterized using morphological, biochemical and molecular biology methods. In order to detect the PHAs granules, the strain of bacteria was first screened with Sudan Black B staining and Nile Blue A staining was done for further confirmation. During the stationary phase, the LMA strain was subjected to 5 % (w/v) of pomegranate molasses (carbon source). Samples were collected for two time of the incubation period for detection of PHAs using Sudan Black B staining. The PHAs production accumulated up to 50.4% of its cell dry weight. The PHAs produced was characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance Spectroscopy (NMR). By using these two methods, it was confirmed that the polymer produced by the isolated bacteria is Polyhydroxybutyrate (PHB) polymer

Plants in Antarctica: current and future phytoremediation potential

As an extremely cold, dry and windy part of the world, Antarctica is a unique continent that can only be inhabit by limited number of organisms. For a long time, Antarctica was a pristine area. But nowadays, it has been invaded with many kinds of pollutants derived from human activities such as solid, liquid and metal wastes. To prevent further deterioration in Antarctic environment, remediation process is strongly needed. Phytoremediation is an environmentally clean technique to remove pollutants using plants. This is an alternative to the current physical and chemical remediation method. The success of phytoremediation technique is influenced by plant species and various environmental parameters. Unlike in the temperate and tropical region, an extremely low temperature in Antarctica does not permit the growth of many types of vegetations. Thus, phytoremediation process is scarce. Despite this limitation, there are growing interests among scientists to investigate the potential of phytoremediation to occur in tremendously harsh condition. This paper reviews current pollution problems in the Antarctic region and the possibility of phytoremediation technique to be implemented in this continen

Cyanide degradation by pseudomonas pseudoalcaligenes strain W2 Isolated from mining effluent

Cyanide is highly toxic to the living organisms as it inhibits respiration system in the cell mitochondria. Cyanide is commonly used in gold extraction process and its discharge into the environment not only causes pollution but it also brings harm to the surrounding population. Chemical treatment is expensive and the use of hazardous compound can exacerbate the problem. Biodegradation offers cheap and safe alternative as it overcomes the problems faced by chemical treatment. In this study, indigenous bacteria from mining wastewater were isolated. Cyanide degradation was done via shake flask method. A bacterium, designated W2 was found able to grow in the mining wastewater. 16S rRNA analysis identified the strain as Pseudomonas pseudoalcaligenes which could tolerate up to 39 mg/L cyanide concentration and growth was depleted at 52 mg/L. 60% cyanide degradation was achieved in wastewater containing medium. End-product analysis from high performance liquid chromatography (HPLC) detected formamide implicating the role of cyanide hydratase in cyanide degradation. It can be concluded that P. pseudoalcaligenes is capable of biodegrading cyanide and its potential in wastewater treatment containing cyanide is feasible

A redox mediated UME biosensor using immobilized chromobacterium violaceum strain R1 for rapid biochemical oxygen demand measurement

An effective ferricyanide-mediated microbial biochemical oxygen demand (BOD) biosensor was constructed and used for BOD determination in a water system. This BOD sensor uses ultramicroelectrode (UME) technology in which the tip of the sensor consists of a two-electrode system (10-µm Pt working electrode and Pt counter electrode). Because of their small size, UMEs have relatively large diffusion layers and small overall currents enabling rapid achievement of useful steady-state conditions with very high scan rates. Living Chromobacterium violaceum R1 cells (isolated from pineapple industry wastewater) were immobilized on the surface of the UME working electrode using a calcium alginate gel and further enclosure by a layer of polyamide membrane. Glucose-glutamic acid (GGA) solution was used as the standard solution. The amperometric measurement was optimized at +450 mV operating potential and 30 mM ferricyanide in a 0.1 M phosphate buffer (pH 7.0) at 26 °C. The sensor exhibited a linear response ranging from 20 to 225 mg O2 L-1 BOD5 for standard GGA solution and 25 to 230 mg O2 L-1 BOD5 for OECD synthetic wastewater with a response time of 30 min. Repeatability and reproducibility of the biosensor were within the limits set by the APHA; i.e., less than 15.4%. The rapid BOD estimation of the biosensor is applicable for measuring samples with a high content of fast and easily assimilated compounds. When used to estimate the BOD of various wastewaters, the developed biosensor provided values comparable to those obtained using the conventional BOD5 method

Histological and proteome analyses of Microbacterium foliorum-mediated decrease in arsenic toxicity in Melastoma malabathricum

Arsenic (As) is an increasing threat across the globe, widely known as a non-threshold carcinogen, and it is reaching harmful values in several areas of the world. In this study, the effect of plant growth promoting bacteria (Microbacterium foliorum) on inorganic arsenic (Arsenate) phytoremediation by Melastoma malabathricum plants was investigated through histological analysis and proteome profiling of the M. malabathricum plants. Two-dimensional gel electrophoresis and transmission electron microscopy were used to conduct the proteome and histological analysis. When arsenic-treated cells were compared to untreated cells, substantial changes were found (1) severely altered the morphology of the cells, intensely disturbed; (2) the cell wall was thicker; (3) drastically changed the cytoplasm, the cells were polygonal in shape, different in size (scattered), and relatively dense. Compared to the control group, the ultra-structure of the root cells of the control group revealed intact cytoplasm, vacuole, and cell wall under exposure to As + bacteria that had a minor effect on the cell form. To further understand As + bacteria interaction, proteome profiling of the root cell was analyzed. The As-induced oxidative stress enrichment was confirmed by the up-regulation of tubulin, nucleoside diphosphate kinase, and major allergen during As + bacteria exposure It was observed that the profusion of proteins involved in defence, protein biogenesis, signaling, photosynthesis, nucleoside and energy metabolism was greater in As + bacteria as compared to the rooting out of As only. Overall, it can be obviously seen that the current study demonstrates the effectiveness of phytoremediation by M. foliorum on proteins involved and responsive pathways in dealing with As toxicity in M. malabathricum plant

Strep-tag ii mutant maltose-binding protein for reagentless fluorescence sensing

Maltose-binding protein (MBP) is a periplasmic binding protein found in Gram negative bacteria. MBP is involved in maltose transport and bacterial chemotaxis; it binds to maltose and maltodextrins comprising α(1-4)-glucosidically linked linear glucose polymers and α(1-4)-glucosidically linked cyclodextrins. Upon ligand binding, MBP changes its conformation from an open to a closed form. This molecular recognition-transducing a ligand-binding event into a physical one-renders MBP an ideal candidate for biosensor development. Here, we describe the construction of a Strep-tag II mutant MBP for reagentless fluorescence sensing. malE, which encodes MBP, was amplified. A cysteine residue was introduced by site-directed mutagenesis to ensure a single label attachment at a specific site with a thiol-specific fluorescent probe. An environmentally sensitive fluorophore (IANBD amide) was covalently attached to the introduced thiol group and analysed by fluorescence sensing. The tagged mutant MBP (D95C) was purified (molecular size, ∼42 kDa). The fluorescence measurements of the IANBD-labelled Strep-tag II-D95C in the solution phase showed an appreciable change in fluorescence intensity (dissociation constant, 7.6±1.75 μM). Our mutant MBP retains maltose-binding activity and is suitable for reagentless fluorescence sensin

Catalyst-free crosslinking modification of nata-de- coco-based bacterial cellulose nanofibers using citric acid

Bacterial cellulose (BC) has gained research attention in materials science and biomedicine due to its fascinating properties. BCs' fiber collapse phenomenon (inability to reabsorb water after dehydration) is one of the drawbacks that limit its potentials. To overcome this, a catalyst-free thermal crosslinking reaction was employed to modify the BC using citric acid (CA) without compromising the biocompatibility. Properties evaluation of the modified BC (MBC) by FTIR, XRD, SEM/EDX, TGA, and Tensile analysis confirmed the fiber crosslinking and improvement of some properties that could be advantageous for various applications. The modified nanofiber seems to maintain its inherent crystallinity and thermal stability with an increased water absorption/swelling and tensile modulus. The resulting MBC reported here can be relevant for wound dressings and tissue scaffolding

Protein engineering of selected residues from conserved sequence regions of a novel Anoxybacillus α-amylase

The α-amylases from Anoxybacillus species (ASKA and ADTA), Bacillus aquimaris (BaqA) and Geobacillus thermoleovorans (GTA, Pizzo and GtamyII) were proposed as a novel group of the α-amylase family GH13. An ASKA yielding a high percentage of maltose upon its reaction on starch was chosen as a model to study the residues responsible for the biochemical properties. Four residues from conserved sequence regions (CSRs) were thus selected, and the mutants F113V (CSR-I), Y187F and L189I (CSR-II) and A161D (CSR-V) were characterised. Few changes in the optimum reaction temperature and pH were observed for all mutants. Whereas the Y187F (t1/2 43 h) and L189I (t1/2 36 h) mutants had a lower thermostability at 65°C than the native ASKA (t1/2 48 h), the mutants F113V and A161D exhibited an improved t1/2 of 51 h and 53 h, respectively. Among the mutants, only the A161D had a specific activity, kcat and kcat/Km higher (1.23-, 1.17- and 2.88-times, respectively) than the values determined for the ASKA. The replacement of the Ala-161 in the CSR-V with an aspartic acid also caused a significant reduction in the ratio of maltose formed. This finding suggests the Ala-161 may contribute to the high maltose production of the ASKA