Biochemical Engineering Journal (v.102, #C)
BEJ Keywords (IV).
Preface: Emerging trends in industrial biotechnology by Indu Shekhar Thakur; Ashok Pandey; P. Nigam; K. Madhavan Nampoothiri (1).
Process optimization of lipase catalyzed synthesis of diesters in a packed bed reactor by Sarbani Ganguly; Sumit Nandi (2-5).
Display OmittedWax esters are fine chemicals which are produced in low volume but are highly priced with varied industrial applications. They are formulated in numerous personal care products due to their excellent emollient properties. The conventional technology for the preparation of wax esters are based on reaction between long chain carboxylic acids and alcohols at high temperatures in presence of a strong catalyst. This process is unselective and the removal of used catalyst and byproducts requires several stages which increases the production cost. Enzyme technology is an alternative which is eco friendly and requires lesser stages of purification. The present study aims at the enzymatic preparation of wax esters like dibehenyl adipate and dibehenyl sebacate in presence of immobilized lipases from different microbial origin e.g., RM-IM, TL IM, NS40013 and NS 435. Various reaction parameters like temperature, reaction time, mole ratio, enzyme concentration and solvent selection were optimized. The work clearly indicates NS 435 as the most efficient enzyme and can be recycled for 20 times without significant change in product quality. Trial run was given in a packed bed bioreactor using NS435 which produced 89% and 91% of dibehenyl adipate and dibehenyl sebacate, respectively.
Keywords: Lipase; Wax esters; Immobilized enzymes; Dibehenyl adipate; Dibehenyl sebacate; Packed bed Bioreactor; Optimisation;
Transglycosylating glycoside hydrolase family 1 β-glucosidase from Penicillium funiculosum NCL1: Heterologous expression in Escherichia coli and characterization by Gurusamy Ramani; Balasubramanian Meera; Jeyaprakash Rajendhran; Paramasamy Gunasekaran (6-13).
A β-glucosidase cDNA belonging to glycoside hydrolase family 1 was cloned from RNA isolated from lactose grown cellulolytic fungus, Penicillium funiculosum NCL1 by reverse-transcriptase polymerase chain reaction. The gene (bgl6) contained an open reading frame of 1470 bp that encoded 490 amino acids. bgl6 gene was overexpressed in Escherichia coli BL21-CodonPlus and the recombinant enzyme (rBgl6) was purified. The rBgl6 was a monomer with the molecular weight of 52 kDa. The enzyme was optimally active at pH 6.0, 50 °C and stable in the wide range of pH and temperature. rBgl6 showed higher activity with pNPG, pNPGal cellobiose and lactose, while it showed substantial activity on pNPX. When the substrate was pNPG, the enzyme showed glucose tolerance at a concentration of 500 mM. rBgl6 exhibited enhanced activity with metal cations Ca2+, Mn2+, Mg2+ and Zn2+, while it showed stability with DTT and EDTA. The enzyme showed K m values of 0.125 and 0.25 mM, whereas V max of 256 and 166 μmol/mg with pNPG and cellobiose respectively. rBgl6 possessed transglycosylation activity and it converted glucose into gentiobiose, a rare oligosaccharide with greater prebiotic value. The yield of gentiobiose was 0.57 mg/ml for 5 mg/ml of glucose. These results indicated that rBgl6 could be a valuable candidate for the enzymatic synthesis of gentiobiose.
Cloning and expression of l-asparaginase from E. coli in eukaryotic expression system by Syed Sajitha; Jalaja Vidya; karunakaran Varsha; Parameswaran Binod; Ashok Pandey (14-17).
l-Asparaginase is an anti-cancer agent which prevents the proliferation of cancerous cells by decreasing the level of asparagine in the blood. l-asparaginase from Escherichia coli which is encoded by ansB gene is widely used because of its substrate specificity and less glutaminase activity. Here, we are reporting the expression studies in yeast which has many added advantages like protein folding and processing. The expression studies were carried out in a new protein expression system based on the yeast Pichia pastoris called PichiaPink™. ansB gene isolated from E. coli which is coded for asparaginase was cloned into pPink HC-α plasmid and transformed into protease knock out pichia pink strain by electroporation. The recombinant enzyme was extracellular and showing the activity of 2.5 IU/ml. It was then purified using Ni-NTA column since the enzyme contains His-tag at the C-terminal end. The new way of expression would be efficient in making the enzyme humanized by glycosylation patterns which is similar to mammals.
Keywords: Enzyme technology; Auxotroph; Submerged culture; Recombinant DNA; Asparaginase; Pichia pink;
Magnetic immobilization and characterization of α-amylase as nanobiocatalyst for hydrolysis of sweet potato starch by G. Baskar; N. Afrin Banu; G. Helan Leuca; V. Gayathri; N. Jeyashree (18-23).
Magnetic immobilization of enzymes became emerging method for efficient recovery of biocatalyst under magnetic field. Sweet potato (Ipomoea batatas) root starch is abundantly produced in tropical countries. Thus the present work was focused on immobilizing α-amylase on to magnetic nanoparticles and use as biocatalyst for hydrolysis of sweet potato starch into glucose. The hydrolysis of sweet potato starch using immobilized α-amylase was investigated and the maximum glucose yield of 42.89 mg/g was obtained using 3% (w/v) of sweet potato starch concentration with an initial pH 4 at 40 °C in 80 min reaction time. The optimal concentration of immobilized α-amylase for maximum glucose yield was found as 1% (w/v). The kinetics of hydrolysis reaction was studied using Michaelis–Menten equation. The sweet potato starch was found to have more affinity towards magnetically immobilized α-amylase with substrate affinity constant (Km) of 0.16 mg/ml and the maximum reaction rate (V max) of 3.63 × 10−3 μmol/ml s. The magnetically immobilized nanocomposite of α-amylase can be easily recovered and reused for maximum utilization.
Keywords: Immobilisation; Amylase; Characterization; Enzyme biocatalysis; Sweet potato starch; Enzyme kinetics;
Production of an alkaline xylanase from recombinant Kluyveromyces lactis (KY1) by submerged fermentation and its application in bio-bleaching by Leya Thomas; Raveendran Sindhu; Parameswaran Binod; Ashok Pandey (24-30).
The aim of this work was to study the production of recombinant xylanase using a Kluyveromyces lactis GG799 strain with a plasmid vector pKLAC1 carrying xylanase coding gene (XynA) isolated from Bacillus pumilus MTCC 5015. To obtain maximum xylanase expression, statistical approaches based on response surface methodology (RSM) was employed. Critical variables for recombinant xylanase production were identified by one-variable-at- a- time approach followed by response surface methodology (RSM), which led to an enhancement in extracellular xylanase production (200 IU/mL). Maximum xylanase production was obtained when 2% of casamino acid was used along with 5% of galactose (inducer) with an inoculum size of 2.75% (5 × 108 CFU/mL) when incubated for 48 h with a pre-inoculum age of 24 h (273 IU/mL). Thus, a four-fold increase in activity from 70 IU/mL to 273 IU/mL could be achieved. SDS-PAGE analysis showed that the relative molecular mass of glycosylated XynA was about 35.0 kDa. The partially purified enzyme was used for the bio-bleaching of paper carton, which showed its effective application in bleaching.
Keywords: Bio-bleaching; Fermentation; Enzymes; Yeast; Purification;
Signal peptides from filamentous fungi efficiently mediate the secretion of recombinant proteins in Kluyveromyces lactis by Aravind Madhavan; Rajeev K. Sukumaran (31-37).
Kluyveromyces lactis is an established host for the secretory production of heterologous proteins. The secretion of enhanced green fluorescent protein (EGFP) in K. lactis mediated by nine secretion signals originating from different filamentous fungi – Aspergillus niger, Aspergillus nidulans, Aspergillus terreus, Aspergillus awamori and Trichoderma reesei were investigated. EGFP was fused to the carboxyl terminus of signals and was expressed under the control of the lac4 promoter. In all the cases, EGFP was secreted into the extracellular fluid. SDS-polyacrylamide gel electrophoresis, western blot analysis of the culture supernatant, and fluorescence measurements confirmed the efficient secretion of EGFP mediated by the novel secretion sequences. In addition, we confirmed that codon optimization and addition of kex2 protease cleavage site in filamentous fungal signal peptide elevated the expression level of recombinant proteins. Efficiency of fungal signal peptide in secretion of other heterologous proteins was demonstrated through secretion of recombinant human interferon β.
Keywords: Secretion signal; Codon optimization; Heterologous protein; Kex2; Green fluorescent protein;
Current perspectives in enzymatic saccharification of lignocellulosic biomass by Sunil K Khare; Ashok Pandey; Christian Larroche (38-44).
With the depletion of fossil fuel reserves, there is an urgent need to search for renewable and cost effective strategies for biofuel production. Lignocellulosic biomass has been perceived as a potential feedstock, wherein effective pretreatment and saccharification is necessary prerequisite for developing viable biofuel processes. Recent approaches in this context are, (i) studying enzymes from extremophilic organisms, particularly thermophiles which are gaining importance in this aspect as they are found to be stable and catalytically more effective under harsh conditions; (ii) usage of ionic liquids for pretreatment is emerging as a greener technology due to their non toxic nature. Developing/screening for ionic liquid tolerant lignocellulosic enzymes in order to attain simultaneous pretreatment and saccharification, offer an interesting option; and (iii) engineering/manipulating the existing lignocellulosic enzymes for desirable traits and viable saccharification and biofuel generation processes. The review encompasses these approaches and the focus on the recent development in the area.
Keywords: Cellulose; Biofuel; Enzymes; Thermophiles; Extremophiles; Ionic liquids;
An integrative process for bio-ethanol production employing SSF produced cellulase without extraction by Reeta Rani Singhania; Reetu Saini; Mukund Adsul; Jitendra Kumar Saini; Anshu Mathur; Deepak Tuli (45-48).
Display OmittedBio-ethanol production from pretreated biomass in a single vessel was investigated in which cellulase production via SSF by Penicillium janthinellum EMS-UV-8, hydrolysis of biomass and ethanol fermentation was carried out sequentially. In this study, feasibility of using whole fermented matter with enzyme, fungal mycelia, spores and residual substrate, for the saccharification of pretreated wheat straw or avicel and its further fermentation to ethanol was investigated. Whole fermented matter produced during cellulase production via solid-state fermentation and extracted cellulase was compared for hydrolysis efficiency toward cellulosic biomass. Ethanol fermentation by Kluveromyces marxianus MTCC 4136 was investigated for both the above cases and no significant difference was observed. We could obtain similar titers of ethanol by both methods. Employing the whole fermented matter offered advantages over using extracted enzyme by reducing enzyme extraction step and thereby reducing economic constraint.
Keywords: Solid-state fermentation; Cellulase; Bioconversion; Biomass; Ethanol; Whole fermented matter;
Evaluation of Amberlyst15 for hydrolysis of alkali pretreated rice straw and fermentation to ethanol by S. Meena; S. Navatha; B.L.A. Prabhavathi Devi; R.B.N. Prasad; A. Pandey; R.K. Sukumaran (49-53).
Solid acid catalysts are potent alternatives to enzymes or mineral acids currently used in the hydrolysis of lignocellulosic biomass to generate sugars for further applications in biofuel or chemicals manufacturing. They are considered green, environmentally safe, and are reusable. In the present work, Amberlyst 15 was evaluated as a solid acid catalyst for the hydrolysis of alkali pretreated biomass. A response surface methodology was used to optimize the hydrolysis of pretreated rice straw. Optimized conditions of 7.0% biomass and catalyst loading resulted in a sugar yield of 255 mg/g of pretreated biomass in 4.0 h. The catalytic hydrolysate generated lesser amount of fermentation inhibitors compared to similar treatment by mineral acids. Recovery and reusability of the catalyst was also studied. The catalytic hydrolysate could be used for fermentative production of bioethanol. Results indicate the possibility to use solid acid catalysts as an alternative strategy for biomass hydrolysis.
Keywords: Ethanol; Heterogeneous reaction; Optimization; Cellulose; Solid acid catalyst; Catalytic hydrolysis;
Pilot scale pretreatment of wheat straw and comparative evaluation of commercial enzyme preparations for biomass saccharification and fermentation by Ruchi Agrawal; Alok Satlewal; Ruchi Gaur; Anshu Mathur; Ravindra Kumar; Ravi Prakash Gupta; Deepak K. Tuli (54-61).
Conversion of pretreated lignocellulosic biomass (LCB) into sugars is one of the critical steps for bioethanol production. High LCB hydrolysis could be achieved by employing robust enzymes having high inhibitor tolerance, low irreversible lignin binding, and low end-product inhibition. In this study, acid pretreatment of wheat straw was carried out at pilot scale (250 kg/day) and three commercial cellulase preparations from Advanced Enzyme (AD), Novozyme (CL), and Genencor (AC) were evaluated for inhibitor (lignin, furfural, hydroxyl methyl furfural, vanillin) tolerance. Pretreated wheat straw (PWS) hydrolysis was carried out at different enzyme concentrations (1–30 mg protein/g of PWS) under optimum pH and temperature in rolling bottle reactor. Simultaneous saccharification and fermentation was performed employing in-house thermotolerant Saccharomyces cerevisiae. Results indicated that, maximum saccharification (more than 85%) was achieved at low protein loadings (10–15 mg protein/g PWS) of CL and this enzyme was also found to be more robust in presence of inhibitors. Maximum ethanol yield (78%) was found at 20 mg protein/g of PWS using CL. This study suggests that inhibitors have significant detrimental effect on enzymes and better understanding of enzyme-inhibitor correlation with its critical moderation would help in further enhancing the LCB hydrolysis at low enzyme dosage.
Keywords: Pretreatment; Saccharification; Enzyme inhibitors; Lignin; Thermotolerant yeast;
Genetically encoded FRET-based nanosensor for in vivo monitoring of zinc concentration in physiological environment of living cell by Mohd. Mohsin; Hema Diwan; Ishrat Khan; Altaf Ahmad (62-68).
Heavy metals are ubiquitous in nature, thus constituting a serious environmental problem in many countries. Due to their toxicity, there is an obvious need to determine them at trace levels. Zinc is essential for many cellular processes, including DNA synthesis, transcription, and translation, but excess can be toxic. To analyze the uptake and metabolism of zinc in Escherichia coli, a high affinity FRET (Fluorescence Resonance Energy Transfer)–based nanosensor was developed using the cyanobacterial metallothionein SmtA flanked by CFP (cyan fluorescent protein) and YFP (yellow fluorescent protein). The chimeric sensor protein was expressed in E. coli BL21 (DE3) and purified by affinity chromatography. Following binding of zinc, FRET ratio increased with increasing the Zn2+ concentration. Affinity mutants were constructed with binding constants ranging from 50 μM to 1 mM. In vitro analysis with bacterially purified sensor showed that it is specific for Zn2+ and responds only weakly to Cd2+ with no response for other biological metal ions. Moreover, the sensor activity in vitro was stable with extreme changes in pH. In vivo analysis of nanosensor response in E. coli showed that free Zn2+ accumulate in the bacterial cells and is slowly metabolized.
Keywords: Zinc; FRET; Recombinant DNA; Sensors; Purification; Protein;
Enzyme-free and biocompatible nanocomposite based cholesterol sensor by Nidhi Joshi; Kamla Rawat; Pratima R Solanki; H.B. Bohidar (69-73).
Display OmittedWe have systematically probed the gelation phenomenon of the mixed clay Laponite (L)–Montmorillonite (MMT) in aqueous dispersion (L:MMT = 1:1). The structurally better and functionally advanced material, so produced, allowed the possibility of formation of homogeneous thin gel films that had good thermo-mechanical properties and transparency. This nanocomposite gel was deposited onto indium tin oxide (ITO) coated glass plates via drop casting method to produce sensor electrodes. The structural and morphological studies of these L-MMT/ITO electrodes were characterized by electrochemical technique. The redox behavior of this electrode towards ascorbic acid (AA), oxalic acid (OA), glucose (Glu) and cholesterol (ChO) was investigated by cyclic voltammetry. The electrochemical response of these electrodes was monitored with different metabolites in the concentration range 1–20 mM. This response showed a broad range of linearity and higher sensitivity for cholesterol, in particular. The excellent electro-catalytic behavior of L-MMT/ITO electrode may find application in the construction of strip-based sensor for detection of cholesterol in particular that too in an enzyme-free platform.
Keywords: Nanocomposites; Enzyme-free; Multianalyte; Sensor; Mixed clay; Cyclic voltammetry;
Chitosan: Emergence as potent candidate for green adhesive market by Anil Kumar Patel (74-81).
Chitosan has gained significant attention during last decades as a potent natural adhesive. Its lower concentrations (<10% w/v) offer competitive strength as synthetic adhesives which would reduce economic constrains of adhesive production. There is increasing commercial interest on chitosan as it possesses biodegradability, biocompatibility, non-toxicity and anti-microbial properties which are of high interest for industries and consumers. Moreover, it has reactive amino side groups, which offer possibilities of chemical modification, increased ionic interactions and graft-reactions etc. Degree of deacetylation (DD) and molecular weight (Mw) is important in bonding mechanism. Most of the synthetic adhesives are comprised of petrochemicals that leave toxic residues such as formaldehyde and volatile organic compounds (VOCs), which are injurious to health and environment. Therefore, development of cost-effective, environmental and health-friendly green adhesives, based on renewable resources is main interest of adhesive industries these days. Rising oil prices are another driving force in research for development of bioadhesives as substitute of synthetic adhesives. This review is focused on current developments of chitosan adhesives for structural and general bonding applications during last decades as well as its current market potential worldwide.
Keywords: Chitosan; Adhesive; Absorption; Glucose; Glycerol; Proteins;
Statistical optimization of cassava fibrous waste hydrolysis by response surface methodology and use of hydrolysate based media for the production of optically pure d-lactic acid by Satish Cingadi; Katla Srikanth; Arun E.V.R; Senthilkumar Sivaprakasam (82-90).
Cassava fibrous waste (CFW), generated as a solid waste by the sago industries in India, is rich in starch. CFW may cause environmental pollution when disposed improperly. Such a waste is used as feedstock, on hydrolysis, for production of optically pure d-lactic acid (DLA) by lactic acid bacteria (LAB). Statistical optimization of hydrolysis (acid and enzymatic hydrolysis) of CFW by the response surface methodology showed enzymatic hydrolysis to be the best method to obtain a maximum glucose yield (69.9 g/L) compared to that obtainable from acid hydrolysis (24.7 g/L). Lactobacillus delbrueckii subsp. delbrueckii (NBRC 3202) (DLA concentration = 2.9 g/L, optical purity = 97.87%, Y P/S = 0.35, Y X/S = 0.30) is selected from eight strains of the homo-fermentative LAB with the shake flask experimental studies in MRS medium. Results from the shake flask experimental studies confirm that the CFW enzyme-hydrolysate is a suitable carbon source (DLA concentration = 4.5 g/L, optical purity = 98.02%, Y P/S = 0.61, Y X/S = 0.42) and yeast extract is a suitable nitrogen source (DLA concentration = 3.16 g/L, optical purity = 97.33%, Y P/S = 0.71, Y X/S = 0.151) for the production of DLA by L. delbrueckii subsp. delbrueckii. Results from the bioreactor experimental studies for production of DLA by L. delbrueckii subsp. delbrueckii in the media with the CFW enzyme-hydrolysate as the carbon source, yeast extract as the nitrogen source, show higher productivity on anaerobic fermentation (r P = 0.90 g/L/h) than aerobic fermentation (r P = 0.78 g/L/h).
Keywords: Optimization; Glucose; Kinetic parameters; Lactic acid; Cassava fibrous waste; Lactobacillus;
Robust and fluorescent silver nanoparticles using Artemisia annua: Biosynthesis, characterization and antibacterial activity by Nafeesa Khatoon; Razi Ahmad; Meryam Sardar (91-97).
Display OmittedMetal nanoparticles have been studied extensively because of their unique physicochemical properties. Among the metal nanoparticles, silver nanoparticles have gained much interest over the last few years due to its good conductivity, chemical stability, catalytic and antimicrobial activity. In this study, fluorescent silver nanoparticles were synthesized using Artemisia annua leaf extract. After exposing the silver ions to the leaf extract, the rapid reduction of silver ions led to the formation of silver nanoparticles in solution. The synthesis was completed within 5 min. The synthesized fluorescent silver nanoparticles were characterized by UV–vis, fluorescence spectroscopy TEM, EDX, XRD, and FTIR. The antibacterial activity of the nanoparticles against gram negative and gram positive bacterial strains were studied. The antibacterial effect was studied by MIC and disk diffusion assay. The stability of fluorescent silver nanoparticles in biological media was demonstrated with the resistance to oxidation by the addition of H2O2. TEM analysis of fluorescent silver nanoparticles treated bacterial cells reveals that the silver nanoparticles exert antibacterial activity by disrupting the cell membrane structure and integrity. The biosynthesized silver nanoparticles were biocompatible which were confirmed by checking the cytotoxicity against human erythrocytes. The silver nanoparticles showed significant fluorescence and antibacterial activity, indicating that has the potential to be used in the development of value-added products in the biomedical and nanotechnology-based industries.
Keywords: Artemisia annua; Antibiotic; Biosynthesis; Cell disruption; Fluorescence; Microbial growth;
Partial loss of self-resistance to daunorubicin in drrD mutant of Streptomyces peucetius by Kattusamy Karuppasamy; Padmanabhan Srinivasan; Balasubramaniem Ashokkumar; Rahul Tiwari; Karuppiah Kanagarajadurai; Ranjan Prasad (98-107).
Display OmittedSelf-resistance is a key element for survival of antibiotic producing Streptomyces. Self-resistance in Streptomyces peucetius is conferred by drrA, drrB and drrC genes to survive the toxicity of daunorubicin produced by the organism. The fourth gene is drrD, which is found in drrAB operon and was reported as a possible self-resistance gene. In this study, a drrD mutant is constructed, which showed loss of self-resistance partially to daunorubicin. This study establishes drrD gene as self-resistance gene and along with drrA, drrB and drrC it forms the full complement of self-resistance that protects S. peucetius from the toxicity of daunorubicin. Bioinformatics analysis of DrrD protein showed that it has N-terminal FAD binding domain. It belongs to a family of proteins that does oxidoreductase and transferase activity. DrrD shares high similarity with FAD binding AknOx protein of S. galilaeus, the aclacinomycin producer. DrrD protein was expressed and the partially purified protein was able to bind to FAD. AknOx binds to sugar moiety of aclacinomycin and modifies it to a temporary inactive form and similar role for DrrD is discussed.
Keywords: Streptomyces peucetius; Daunorubicin; Modeling; drrD deletion mutant;
Kinetics and biofiltration of dimethyl sulfide emitted from P&P industry by Balendu Shekher Giri; Mandavi Goswami; R.A Pandey; K.H Kim (108-114).
Anaerobic bio-treatment of waste air generated from various industries including pulp and paper (P&P) industry produce biogas containing reduced form of sulfur pollutants such as dimethyl sulfide (DMS) and hydrogen sulfide (H2S). Some of the gaseous emissions containing DMS are also generated from several industrial wastes which are generally incinerated with high energy input. In the present investigation, a potential DMS degrading microorganism Bacillus sphaericus was isolated from garden soil near a P&P industry for biodegradation. Waste gas containing DMS has been treated in a hybrid biofilter system up to 70% removal efficiency, at an optimal load of 17.3 g/m3/h1 and an optimum effective bed contact time (EBCT) of 384 s. Growth kinetic for biodegradation was also evaluated through flask culture experiments. The values of the different biokinetic parameters for K s, μ max, degradation of substrate (K) and Y were obtained as 0.022 g/m3 , 0.0057 h−1 0.013 h−1 and 0.0022, respectively. The relevance in the context of DMS biodegradation is discussed.
Keywords: Anaerobic treatment; Biofilters; Biodegradation; Bioremediation; Biokinetics; Removal efficiencies;
Biodegradation of wastewater organic contaminants using Serratia sp. ISTVKR1 isolated from sewage sludge by Asmita Gupta; Indu Shekhar Thakur (115-124).
Wastewater was collected from various stages and sewage sludge was collected from sludge bed of Vasant Kunj sewage treatment plant (VK STP) in the post-monsoon season. The treatment plant is based on extended aeration activated sludge (EAAS) process. Preliminary analysis of the wastewater and sewage sludge samples revealed 11.5 fold reduction in chemical oxygen demand (COD) of wastewater after treatment while GC–MS analysis showed the presence of bisphenol P (RT = 41.63), certain pharmaceuticals, pesticides, and industrial compounds in effluent and sewage sludge, thus indicating the need for further treatments before their discharge into the environment. One indigenous bacterial strain isolated from sewage sludge of VK STP and identified as Serratia sp. ISTVKR1 was used for biodegradation of wastewater contaminants. Preliminary analysis of bacterial treatment culture showed almost 12 fold COD removal after 240 h of treatment while the GC–MS analysis revealed removal of complex organic compounds like phosphoric acid triphenyl ester (RT = 30.017) and 4H-1-benzopyran-4-one, 2-(3,4-dimethoxyphenyl)-3,5-dihydroxy-7-methoxy- (RT = 45.36) and formation of simpler compounds like alcohols and aliphatic hydrocarbons such as 1-heptacosanol (RT = 32.66), docosane (RT = 34.18) and hexadecane (RT = 29.621). Results of the study indicate the efficient removal of wastewater organic contaminants by the isolated Serratia sp. ISTVKR1.
Keywords: Biodegradation; Waste-water treatment; Aeration; Chromatography; Serratia sp; Sewage sludge;
Mapping atrazine and phenol degradation genes in Pseudomonas sp. EGD-AKN5 by Pooja Bhardwaj; Abhinav Sharma; Sneha Sagarkar; Atya Kapley (125-134).
Bacterial isolates with multi-substrate degradation capacities are good candidates for bioremediation of environmental niches. Lab isolate Pseudomonas sp. EGD-AKN5 was found to degrade atrazine, benzoate, phenol, toluene and catechol at the rate of 1.88 ± 0.01, 16.5 ± 1.37, 9.08 ± 2.20, 3.86 ± 0.11, and 3.3 ± 0.29 mg L−1 h−1, respectively. Draft genome sequence analysis demonstrated the presence of the complete degradation pathway for atrazine and phenol. Gene annotation results indicated that atrazine was degraded via the chlorohydrolase route with atzA/B/C/D/E/F genes, while phenol was converted to catechol via a multicomponent phenol hydroxylase from the phc pathway. Genes from the ortho pathway were responsible for the further biodegradation of catechol; a result that was confirmed by enzyme assays. A model to describe the growth and biodegradation of atrazine, phenol and related compounds was applied and fit to a series of aerobic batch degradation experiments. Kinetic studies revealed that EGD-AKN5 showed potential to degrade both phenol and atrazine simultaneously using phenol as the carbon source and atrazine as nitrogen source. Gene expression studies indicated a longer lag phase for expression of genes from the atrazine degradation pathway, when compared to expression of phenol and catechol degradation.
Keywords: Atrazine; Bioremediation; Draft genome; Enzyme activity; Growth kinetics; Phenol;