MiDAS 5: Global diversity of bacteria and archaea in anaerobic digesters.

Anaerobic digestion of organic waste into methane and carbon dioxide (biogas) is carried out by complex microbial communities. Here, we use full-length 16S rRNA gene sequencing of 285 full-scale anaerobic digesters (ADs) to expand our knowledge about diversity and function of the bacteria and archaea in ADs worldwide. The sequences are processed into full-length 16S rRNA amplicon sequence variants (FL-ASVs) and are used to expand the MiDAS 4 database for bacteria and archaea in wastewater treatment systems, creating MiDAS 5. The expansion of the MiDAS database increases the coverage for bacteria and archaea in ADs worldwide, leading to improved genus- and species-level classification. Using MiDAS 5, we carry out an amplicon-based, global-scale microbial community profiling of the sampled ADs using three common sets of primers targeting different regions of the 16S rRNA gene in bacteria and/or archaea. We reveal how environmental conditions and biogeography shape the AD microbiota. We also identify core and conditionally rare or abundant taxa, encompassing 692 genera and 1013 species. These represent 84-99% and 18-61% of the accumulated read abundance, respectively, across samples depending on the amplicon primers used. Finally, we examine the global diversity of functional groups with known importance for the anaerobic digestion process.

A sustainable activated carbon fiber/TiO2 cathode for the photoelectro-Fenton treatment of pharmaceutical pollutant enalapril.

In this work, a TiO2-decorated electrode was fabricated by dip coating activated carbon fibers (ACF) with TiO2, which were then used as a cathode for the photoelectro-Fenton (PEF) treatment of the pharmaceutical enalapril, an angiotensin-converting enzyme inhibitor that has been detected in several waterways. The TiO2 coating was found to principally improve the electrocatalytic properties of ACF for H2O2 production via the 2-e- O2 reduction, in turn increasing enalapril degradation by PEF. The effect of the current density on the mineralization of enalapril was evaluated and the highest TOC removal yield (80.5% in 3 h) was obtained at 8.33 mA cm-2, in the presence of 0.5 mmol L-1 of Fe2+ catalyst. Under those conditions, enalapril was totally removed within the first 10 min of treatment with a rate constant k = 0.472 min-1. In contrast, uncoated ACF only achieved 60% of TOC removal in 3 h at 8.33 mA cm-2. A degradation pathway for enalapril mineralization is proposed, based on the degradation by-products identified during treatment. Overall, the results demonstrate the promises of TiO2 cathodes for PEF, a strategy that has often been overlooked in favor of photoelectrocatalysis (PEC) based on TiO2-modified photoanodes.

Diversity and functional annotation of microorganisms in anaerobic chamber treating nitrate-rich wastewater.

The vertical flow constructed wetlands (VFCW) for the treatment of domestic wastewater has become a conventional and cost effective treatment system with one of the major disadvantage of elevated nitrate concentrations. The present study makes an effort in providing a new design of anaerobic denitrification unit termed as anaerobic chamber (AC) which was introduced after two-stage VFCW to remove nitrates from the treated wastewater (WW). The AC provided all the essential conditions of effective denitrification such as anaerobic environment with enough carbon and nitrogen source. To understand the pollutant removal mechanism in AC, microbial diversity and functional annotation was studied by metagenomic analysis of sequences obtained from biofilm formed in AC. The efficiency of AC was measured with respect to physicochemical wastewater quality parameters. The removal efficiencies were 88, 65, 43 and 27% for total nitrogen, nitrate (NO3), ammoniacal-nitrogen (NH4) and ortho-phosphate respectively. The microbial flora was much more diverse and unique pertaining to anaerobic microbes in AC compared to WW with total of 954 and 1191 genuses respectively with minimum abundance of 10 hits. The metagenomes exhibited 188% more Archaea in the AC than WW where Crenarchaeota, Euryarchaeota, Korarchaeota, Nanoarchaeota and Thaumarchaeota were major phyla with 60 genuses. The nitrogen metabolism was reported in terms of assimilatory nitrate reductase. As the class, Proteobacteria, Actinobacteria were prominent in WW, whereas Proteobacteria, Chloroflexi in AC were abundant. From functional annotation of sequences, the microbial flora in AC has the potential of removal of pollutants present in the form of carbon, nitrogen, and phosphorus.

A novel and sustainable approach for biotransformation of phosphogypsum to calcium carbonate using urease producing Lysinibacillus sphaericus strain GUMP2.

Phosphogypsum (CaSO4) is produced as a waste by-product during phosphoric acid production in the fertilizer industry. Only 15% of worldwide phosphogypsum production is recycled, while 85% is stored in the vicinity of factories as huge piles resulting in environmental and health hazards. An extensively studied biotransformation of phosphogypsum to calcium carbonate or calcite (CaCO3) using sulfate reducing bacteria (SRBs) is a prolonged process and results in the formation of extremely hazardous H2S gas. Here we report for the first time a novel approach for biotransformation of phosphogypsum to CaCO3 using urease producing Lysinibacillus sphaericus strain GUMP2. The strain could effectively transform phosphogypsum to crystalline, bead-shaped CaCO3 precipitates. In a batch reactor with the PG loading rate of 60 g/L, 100% biotransformation was observed within seven days. After calcite recovery, the ammonium sulfate formed in the supernatant was recovered by precipitation. Urease-producing L. sphaericus strain GUMP2 could be used to remove the hazardous phosphogypsum from the environment by converting it to the industrially useful CaCO3 and ammonium sulfate, a valuable agricultural fertilizer. This novel and sustainable approach could be a promising solution for the hazardous phosphogypsum in the phosphoric acid industries.

Probing the degradation of pharmaceuticals in urine using MFC and studying their removal efficiency by UPLC-MS/MS.

Nutrient recovery from source-separated human urine has attracted interest as it is rich in nitrogen and phosphorus that can be utilized as fertilizer. However, urine also contains pharmaceuticals, steroid hormones, etc. and their removal is crucial as they have detrimental effects on the environment and human health. The current study focuses on investigating the degradation of pharmaceuticals using a double-chamber microbial fuel cell (MFC). Urine was spiked with four pharmaceuticals (trimethoprim, lamivudine, levofloxacin, and estrone) at a concentration of 2 µg/mL. The MFC was operated for 7 months in batch mode with this spiked urine as feed. The degradation efficiency of the MFC was studied, for which a selective liquid chromatography-tandem mass-spectrometric method was developed for the quantitation of compounds used in the spiking experiments and was validated with a lower limit of quantification of 0.39 ng/mL. The maximum removal rate achieved was 96% ±â€¯2%. The degradation mechanism involved processes like sorption and anoxic biodegradation. The voltage curve obtained showed that the presence of pharmaceuticals had an initial negative impact on power generation along with increased organic content; however, after the reactor acclimatization, increased power output was achieved with maximum organics removal at 30 h of retention time. This work opens a new perspective for the anoxic biodegradation of pharmaceuticals and can be useful in future bioremediation studies.

Domestic wastewater treatment by constructed wetland and microalgal treatment system for the production of value-added products.

The main aim of this study is to treat domestic wastewater in a hybrid Vertical Flow Constructed Wetland (VFCW-4.2 m2) and Microalgal Treatment System (MTS-1 m2). The objective is not only to treat Domestic wastewater (DW) but also to produce value-added products from microalgal biomass. The domestic wastewater was initially treated by VFCW and the VFCW effluent was further phycoremediated by MTS. Canna indica was used for wetland vegetation and resident microalgal consortium from VFCW effluent was used in MTS. The VFCW and MTS was operated at 1 m3/day (HRT-0.25 m3/m2-day, OLR-400 g/m2-day) and 0.03 m3/day (HRT-0.03 m3/m2-day, OLR-400 g/m2-day), respectively. The integrated system was observed to remove 68.9% COD, 77.4% NH4-N, 75.8% TKN and 63.6% PO4-P. The harvested Naive Biomass (NB) was observed to contain 16.7% of lipids (W/W). The Residual Biomass after Lipid Extraction (RBLE) was used as a substrate for ethanol production. The observed yield of ethanol using RBLE as a substrate was 33.4%. NB, RBLE, and Residual Biomass after Lipid and Sugar Extraction (RBLSE) indicated net biomethane yield (mL/g VS) of 211.8, 134.6 and 107.7, respectively. The present study demonstrated an initial attempt of demonstrating a hybrid wastewater treatment system for the production of value-added products in terms of biofuel.

Diversity and functional annotation of microorganisms in French vertical flow constructed wetland treating greywater.

Constructed wetlands form a unique ecosystem having plants, soil, microbes in which microorganisms play a vital role in the transformation and degradation of pollutants from wastewater. In the present study, French type two-stage vertical flow constructed wetland (VFCW) was used for the treatment of single household greywater (GW). Pilot-scale VFCW having sand and gravel as the filter substrate was constructed with Canna indica plantation for treating GW. To understand the pollutant removal mechanism in VFCW, microbial diversity and functional annotation was carried out by metagenomics analysis of sequences obtained from illumina platform. Efficiency of VFCW was measured with respect to water quality parameters like COD, BOD5, Total Nitrogen, Nitrate, Nitrite, Ammoniacal-N, ortho-phosphate and TOC from inlet and outlet of system. The removal efficiency was 90%, 93%, 34%, 26%, 89%, 68%, 80%, and 80% for COD, BOD5, Total Nitrogen, Nitrate, Nitrite, Ammoniacal-N, ortho-phosphate and TOC respectively. Microbial diversity was much more diversified and unique in VFCW compared to GW. Metagenomes exhibited Proteobacteria and Bacteroidetes as major phyla in GW whereas Actinobacteria, Proteobacteria, Nitrospirae abundance in VFCW layers. Total of 809 and 695 genus were found in VFCW and GW respectively with minimum abundance of 10 hits. From functional annotation of sequences, VFCW microbes have the potential to transform various aromatic and xenobiotic compounds along with the removal of pollutants present in the form of Carbon, Nitrogen, and Phosphorus. These data reveal French type VFCW can efficiently treat GW and with its own unique, variable habitat VFCW harbours diverse community of microorganisms that transform and degrade the pollutants in GW.

Nutrient recovery and microbial diversity in human urine fed microbial fuel cell.

Presence of urine in municipal wastewater is a major problem faced by wastewater treatment plants. The adverse effects are noticeable as crystallization in equipment and pipelines due to high concentration of nitrogen and phosphorus. Therefore, improved technologies are required that can treat urine separately at the source of their origin and then discharge it in the main wastewater stream. In this study, the performance of the microbial fuel cell (MFC) was evaluated with mixed consortia and isolated pure cultures (Firmicutes and Proteobacter species) from biofilm for electricity generation and nutrient recovery. Microbes utilize less than 10% of total phosphorus for their growth, while 90% is recovered as struvite. The amount of struvite recovered was similar for pure and mixed culture (12 ± 5 g/L). The microbial characterization also shows that not all the biofilm-forming bacterial isolates are very much efficient in power generation and, hence, they can be further exploited to study their individual role in operating MFC. The different organic loading rates experiment shows that the performance of MFC in terms of power generation is the same for undiluted and five times diluted urine while the recovery of nutrients is better with undiluted urine, implying its direct use of urine in operating fuel cell.

UPLC-MS/MS method validation of ciprofloxacin in human urine: Application to biodegradability study in microbial fuel cell.

To enable the reliable quantification of ciprofloxacin in human urine, a sensitive and selective assay based on liquid chromatography-tandem mass spectrometry was developed. The chromatographic separation of the ciprofloxacin was carried out on a Zorbex Eclipse C18 column using methanol and ammonium acetate as a mobile phase by the gradient elution method. The developed assay covered a wide range of concentrations (1.56-100 ng/mL) with a lower limit of detection of 0.76 ng/mL. Quantification was performed using the multiple reaction monitoring transitions 331.8/231 for ciprofloxacin and 362/318 for ofloxacin (internal standard). This assay was validated for linearity, accuracy, precision and recovery. The validated method was then applied to the biodegradability of ciprofloxacin (99%) from human urine in the microbial fuel cell.

Silica - A trace geogenic element with emerging nephrotoxic potential.

Silica is a trace-geogenic compound with limited-bioavailability. It inflicts health-perils like pulmonary-silicosis and chronic kidney disease (CKD), when available via anthropogenic-disturbances. Amidst silica-imposed pathologies, pulmonary toxicological-mechanisms are well-described, ignoring the renal-pathophysiological mechanisms. Hence, the present-study aimed to elucidate cellular-cum-molecular toxicological-mechanisms underlying silica-induced renal-pathology in-vitro. Various toxicity-assessments were used to study effects of silica on the physiological-functions of HK-cells (human-kidney proximal-tubular cells - the toxin's prime target) on chronic (1-7 days) sub-toxic (80 mg/L) and toxic (100-120 mg/L) dosing. Results depicted that silica triggered dose-cum-time dependent cytotoxicity/cell-death (MTT-assay) that significantly increased on long-term dosing with ≥100 mg/L silica; establishing the nephrotoxic-potential of this dose. Contrarily, insignificant cell-death on sub-toxic (80 mg/L) dosing was attributed to rapid intracellular toxin-clearance at lower-doses preventing toxic-effects. The proximal-tubular (HK-cells) cytotoxicity was found to be primarily mediated by silica-triggered incessant oxidative-stress (elevated ROS).·This enhanced ROS inflicted severe inflammation and subsequent fibrosis, evident from increased pro-inflammatory-cum-fibrogenic cytokines generation (IL-1ß, IL-2, IL-6, TNF-α and TGF-ß). Simultaneously, ROS induced persistent DNA-damage (Comet-assay) that stimulated G2/M arrest for p53-mediated damage-repair, aided by checkpoint-promoter (Chk1) activation and mitotic-inducers (i.e. Cdc-25, Cdk1, cyclinB1) inhibition. However, DNA-injuries surpassed the cellular-repair, which provoked the p53-gene to induce mitochondrial-mediated apoptotic cell-death via activation of Bax, cytochrome-c and caspase-cascade (9/3). This persistent apoptotic cell-death and simultaneous incessant inflammation culminated in the development of tubular-atrophy and fibrosis, the major pathological-manifestations of CKD. These findings provided novel-insights into the pathological-mechanisms (cellular and molecular) of silica-induced CKD, inflicted on chronic toxic-dosing (≥100 mg/L).Thereby, encouraging the development of therapeutic-strategies (e.g. anti-oxidant treatment) for specific molecular-targets (e.g. ROS) to retard silica-induced CKD-progression, for reduction in the global-CKD burden.

Deleterious role of trace elements - Silica and lead in the development of chronic kidney disease.

Chronic-Kidney-Disease of Unknown-etiology (CKDu) has been reported in developing-countries like Sri-Lanka, India and Central-America without sparing the Indian sub-district (namely Canacona) located in south-Goa. The disease etiology is unlinked to common causes of diabetes and hypertension and assumed to be environmentally induced due to its asymptomatic-nature and occurrence in groundwater relying communities. This study aimed to understand environmental risk-factors underlying CKDu-etiology using Indian sub-district (Canacona) as case-study. Biochemical-analysis of CKDu-affected and non-affected individual's blood and detailed hydro-geochemical analyses of CKDu-affected and non-affected region's groundwater (drinking-water)were conducted. Trace geogenic-element-silica was highly dominant in affected-region's groundwater, thus its nephrotoxic-potential was analysed via in-vitro cytotoxicity-assays on human-kidney-cell-lines. All CKDu-affected-subjects showed increased-levels of serum-urea (52.85 mM),creatinine (941.5 µM),uric-acid (1384.5 µM), normal blood-glucose (4.65 mM), being distinct biomarkers of environmentally-induced CKD-'chronic-tubulo-interstitial-nephritis'. Affected-subjects reported high blood-lead levels (1.48 µM)suggesting direct-nephrotoxicity resulting in impaired blood-clearance and also exhibits indirect-nephrotoxicity by disrupting calcium-homeostasis causing skeletal-disorders and prolonged-consumption of NSAID's (pain-alleviation), indirectly causing renal-damage. Affected-region's groundwater was acidic (pH-5.6), resulting in borderline-lead (9.98 µgL-1) and high-silica (115.5 mgL-1)contamination. Silica's bio-availability (determining its nephrotoxicity) was enhanced at groundwater's acidic-pH and Ca-Mg-deficient-composition (since these cations complex with silica reducing bioavailability). Silica exhibited renal-proximal-tubular-cytotoxicity on long-term exposure comparable with affected-region's groundwater silica-levels, by apoptosis-mediated-cell-death resulting in tubular-atrophy, interstitial-fibrosis and irreversible renal-damage (CKD). Thus this study provides novel-insights into nephrotoxic-potential of trace-geogenic-element-silica in CKDu causation. It highlights direct-indirect nephrotoxicity exhibited by lead at low-levels due to its bio-accumulative-capacity. Silica's nephrotoxic-potential can be considered when deciphering etiology of CKDu-problem in developing-countries (relying on groundwater).

Horizontal gene transfer versus biostimulation: A strategy for bioremediation in Goa.

Bioaugmentation, Biostimulation and Horizontal gene transfer (HGT) of catabolic genes have been proven for their role in bioremediation of hydrocarbons. It also has been proved that selection of either biostimulation or bioremediation varies for every contaminated site. The reliability of HGT compared to biostimulation and bioremediation was not tested. The present study focuses on reliability of biostimulatiion, bioaugmentation and HGT during biodegradation of Diesel oil and Non aqueous phase liquids (NAPL). Pseudomonas aeruginosa (AEBBITS1) having alkB and NDO genes was used for bioaugmentation and the experiment was conducted using seawater as medium. Based on Gas chromatography results diesel was found to be degraded to 100% in both presence and absence of AEBBITS1. Denturing gradient gel electrophoresis result showed same pattern in presence and absence of AEBBITS1 indicating no HGT. NAPL degradation was found to be more by Biostimulated Bioaugmentation compared to biostimulation and bioaugmentation alone. This proves that biostimulated bioaugmentation is better strategy for oil contamination (tarabll) in Velsao beach, Goa.

Pilot project at Hazira, India, for capture of carbon dioxide and its biofixation using microalgae.

The objective of the present study was to set up a small-scale pilot reactor at ONGC Hazira, Surat, for capturing CO2 from vent gas. The studies were carried out for CO2 capture by either using microalgae Chlorella sp. or a consortium of microalgae (Scenedesmus quadricauda, Chlorella vulgaris and Chlorococcum humicola). The biomass harvested was used for anaerobic digestion to produce biogas. The carbonation column was able to decrease the average 34 vol.% of CO2 in vent gas to 15 vol.% of CO2 in the outlet gas of the carbonation column. The yield of Chlorella sp. was found to be 18 g/m2/day. The methane yield was 386 l CH4/kg VSfed of Chlorella sp. whereas 228 l CH4/kg VSfed of the consortium of algae.

Anaerobic co-digestion of sewage sludge and food waste.

Anaerobic co-digestion of organic matter improves digester operating characteristics and its performance. In the present work, food waste was collected from the institute cafeteria. Two types of sludge (before centrifuge and after centrifuge) were collected from the fluidised bed reactor of the institute treating sewage wastewater. Food waste and sludge were studied for their physico-chemical characteristics, such as pH, chemical oxygen demand, total solids, volatile solids, ammoniacal nitrogen, and total nitrogen. A biomethane potential assay was carried out to find out the optimum mixing ratio of food waste and sludge for anaerobic co-digestion. Results indicated that food waste mixed with sludge in the ratio of 1:2 produced the maximum biogas of 823 ml gVS(-1)(21 days) with an average methane content of 60%. Batch studies were conducted in 5 L lab-glass reactors at a mesophilic temperature. The effect of different substrate loading rates on biogas production was investigated. The mixing ratio of food waste and sludge was 1:2. A loading rate of 1 gVS L d(-1)gave the maximum biogas production of 742 ml g(-1)VS L d(-1)with a methane content of 50%, followed by 2 gVS L d(-1)with biogas of 539 ml g(-1)VS L d(-1) Microbial diversity of the reactor during fed batch studies was investigated by terminal restriction fragment length polymorphism. A pilot-scale co-digestion of food waste and sludge (before centrifuge) indicated the process stability of anaerobic digestion.

Biodegradation of aliphatic hydrocarbons in the presence of hydroxy cucurbit[6]uril.

Aliphatic hydrocarbons are one of the major environmental pollutants with reduced bioavailability. The present study focuses on the effect of hydroxy cucurbit[6]uril on the bioavailability of hydrocarbons. A bacterial consortium was used for biodegradation studies under saline and non-saline conditions. Based on denaturing gradient gel electrophoresis results it was found that the consortium under saline conditions had two different strains. The experiment was conducted in microcosms with tetradecane, hexadecane, octadecane and mixture of the mentioned hydrocarbons as the sole carbon source. The residual hydrocarbon was quantified using gas chromatography every 24h. It was found that biodegradation of tetradecane and hexadecane, as individual carbon source increased in the presence of hydroxy CB[6], probably due to the increase in their bioavailability. In case of octadecane this did not happen. Bioavailability of all three aliphatic hydrocarbons was increased when provided as a mixture to the consortium under saline conditions.

Pretreatment of cottage cheese to enhance biogas production.

This study evaluated the possibility of pretreating selected solid fraction of an anaerobic digester treating food waste to lower the hydraulic retention time and increase the methane production. The study investigated the effect of different pretreatments (thermal, chemical, thermochemical and enzymatic) for enhanced methane production from cottage cheese. The most effective pretreatments were thermal and enzymatic. Highest solubilisation of COD was observed in thermal pretreatment, followed by thermochemical. In single enzyme systems, lipase at low concentration gave significantly higher methane yield than for the experiments without enzyme additions. The highest lipase dosages decreased methane yield from cottage cheese. However, in case of protease enzyme an increase in concentration of the enzyme showed higher methane yield. In the case of mixed enzyme systems, pretreatment at 1 : 2 ratio of lipase : protease showed higher methane production in comparison with 1 : 1 and 2 : 1 ratios. Methane production potentials for different pretreatments were as follows: thermal 357 mL/g VS, chemical 293 mL/g VS, and thermochemical 441 mL/g VS. The average methane yield from single enzyme systems was 335 mL/g VS for lipase and 328 mL/g VS for protease. Methane potentials for mixed enzyme ratios were 330, 360, and 339 mL/g VS for 1 : 1, 1 : 2, and 2 : 1 lipase : protease, respectively.

Biodegradation of crude oil by Pseudomonas aeruginosa and Escherichia fergusonii isolated from the Goan coast.

Petroleum hydrocarbons are major pollutants of the marine environment. Bioremediation is a promising approach for treating such contaminated environments. The present study aims at isolating naturally occurring bacteria from the coast of Goa, India and to study their hydrocarbonoclastic capacity. Pseudomonas aeruginosa and Escherichia fergusonii were isolated from a crude oil-contaminated sediment sample using diesel oil as the sole carbon source. The capability of the enriched culture to degrade crude oil was estimated using microcosm studies under saline conditions. Based on GC-MS analysis, the culture was found to degrade n-alkanes at a higher rate compared to polyaromatic hydrocarbons. It was also found that the culture degraded alkylated polyaromatic hydrocarbons much less than unalkylated ones. Alkanes ranging from C12 to C33 were highly degraded compared to n-C34. This study shows bioremediation of crude oil in saline (3% NaCl) conditions by naturally existing bacteria isolated from the marine environment.

Degradation of anthracene and pyrene supplied by microcrystals and non-aqueous-phase liquids.

Polycyclic aromatic hydrocarbons (PAHs) are worldwide environmental pollutants. Their bioavailability is limited by a low aqueous solubility, which causes specific adaptations in degrading bacteria. To compare bacterial degrading behavior, a study was conducted on the mineralization, metabolization and formation of biomass from (14)C-anthracene by Sphingomonas sp. BA2 compared with those from (14)C-pyrene by Gordonia-like strain BP9 and Mycobacterium gilvum VF1. Different conditions of PAH supply were used in the medium: crystals <0.5 mm, microcrystals <<0.1 mm formed by sonication, or PAH solubilized in 2,2,4,4,6,8,8-heptamethylnonane (HMN) or silicone oil. Anthracene supply by crystals and silicone oil led to similar maximum mineralization rates 33 ng ml(-1) h(-1) and the same amount of mineralization (24%) after 168 h. Microcrystals increased the rates and amounts only slightly. HMN decreased the values to less than one-third. In comparison with crystals, microcrystals increased overall pyrene mineralization by strain BP9 from 53% to 58%, with maximum mineralization rates of 160 ng ml(-1) h(-1) and 166 ng ml(-1) h(-1). Silicone oil heavily increased the rate to 292 ng ml(-1) h(-1) and the amount mineralized to 71%, whereas HMN inhibited the degradation by one order of magnitude. A similar degradation behavior showing lower mineralization rates and extent was observed with strain VF1. However, inhibition by HMN was less pronounced. Sonication, leading to decreased PAH crystal size, increased the mass transfer and mineralization rates. PAH supply by silicone oil led to a much higher mass transfer, which may be due to emulsification of the oil, whereas such effects were not observed with HMN.

Changes in fatty acid composition of Chromohalobacter israelensis with varying salt concentrations.

The adaptation of fatty acid composition of Chromohalobacter israelensis, a euryhalophilic bacterium, grown at different salt concentrations was studied. C. israelensis tolerated NaCl up to concentrations of 20% (w/v) and showed optimal growth at 7% (w/v). Major fatty acids of this bacterium were palmitic acid (16:0), stearic acid (18:0), palmetoleic acid (16:1cisDelta9), and cis-vaccenic acid (18:1Delta11). The salt concentration strongly influenced the fatty acid composition. In the presence of sub-optimal salt concentrations, the degree of saturation decreased, suggesting the importance of salt in maintaining the osmotic balance of the cell with its environment.