Microbial halophilic lipases: A review

Microbial lipases are commercially significant due to their versatile catalytic function of hydrolysis triacylglycerol. Among these, lipases from extremophiles are optimal for industrial application. Halophilic microorganisms living in a high salinity environment, such as the ocean, salt lakes, salt wells, and so on, produce halophilic lipases. In recent decades, many remarkable achievements have been made related to the properties and application of halophilic lipases. This review offers information collected over the last decades on halophilic lipase sources as well as advances in production, factors influencing activity, stability under various conditions, structural characteristics, progress in industrial applications such as food flavor modification, biodiesel production, and waste treatment, to provide theoretical and methodological references for the research in this direction.

Bioprospecting potentials of moderately halophilic bacteria and the isolation of squalene producers from Kuwait sabkha

Sabkhas in Kuwait are unique hypersaline marine environments under-explored for bacterial community composition and bioprospecting. The 16S rRNA sequence analysis of 46 isolates with distinct morphology from two Kuwait sabkhas recovered 11 genera. Phylum Firmicutes dominated these isolates, and Bacillus (32.6%) was recovered as the dominant genera, followed by Halococcus (17.4%). These isolates were moderately halophilic, and some of them showed tolerance and growth at extreme levels of salt (20%), pH (5 and/or 11), and temperature (55 °C). A higher percentage of isolates harbored protease (63.0), followed by DNase (41.3), amylase (41.3), and lipase (32.6). Selected isolates showed antimicrobial activity against E. faecalis and isolated Halomonas shengliensis, and Idiomarina piscisalsi harbored gene coding for dNDP-glucose 4,6-dehydratase (Glu 1), indicating their potential to produce biomolecules with deoxysugar moieties. Palmitic acid or oleic acid was the dominant fatty acid, and seven isolates had some polyunsaturated fatty acids (linolenic or γ-linolenic acid). Interestingly, six isolates belonging to Planococcus and Oceanobacillus genus produced squalene, a bioactive isoprenoid molecule. Their content increased 30-50% in the presence of Terbinafine. The potential bioactivities and extreme growth conditions make this untapped bacterial diversity a promising candidate for future bioprospecting studies.

Dehalogenase-producing halophiles and their potential role in bioremediation

This review aims to briefly describe the potential role of dehalogenase-producing halophilic bacteria in decontamination of organohalide pollutants. Hypersaline habitats pose challenges to life because of low water activity (water content) and is considered as the largest and ultimate sink for pollutants due to naturally and anthropogenic activities in which a substantial amount of ecological contaminants are organohalides. Several such environments appear to host and support substantial diversity of extremely halophilic and halotolerant bacteria as well as halophilic archaea. Biodegradation of several toxic inorganic and organic compounds in both aerobic and anaerobic conditions are carried out by halophilic microbes. Therefore, remediation of polluted marine/hypersaline environments are the main scorching issues in the field of biotechnology. Although many microbial species are reported as effective pollutants degrader, but little has been isolated from marine/hypersaline environments. Therefore, more novel microbial species with dehalogenase-producing ability are still desired.

Retracted: Partial purification and characterization of lipase from locally produced edible oil-seeds and its relevance in industries

Lipase was extracted from germinating seeds of Helianthus annus (Sunflower), Zea mays (Maize), and Brassica compastris (Mustard). The lipolytic activity was assessed using olive oil as substrate at different germination-time and the maximum-activity was obtained after 120 hr. Partial-purification was executed by precipitating the seed-homogenate with varying concentration of ammonium sulfate solution. 80% ammonium sulfate solution showed maximum lipase activity of 5320IUml^-1 , 3500IUml^-1 , 3080IUml^-1 with 9.6, 6.9, and 4.8-fold purification and total protein content of 162, 84, and 60 mg for partially purified enzyme extracts namely SN5, BN5, and MN5, respectively. The optimum temperature and pH observed for hydrolysis of olive oil were 37°C, and 8.0 respectively. Enzyme was found to be stable upto 6 days at 4°C and its activity was stimulated by Ca⁺² ions. Oil-stains removal from cotton fabric was observed to be superior in the presence of lipase and detergent. Moreover, the SN5, BN5, and MN5 lipase increased free fatty acid release upto 4.2, 4.3, and 3.8 mg, respectively than wastewater without treatment of lipase (0.21 mg) and promoted fat hydrolysis to approximately 40, 42, and 48% mass reduction after 6 hr incubation of fat particle at a concentration of 20 mg/ml. Biodiesel produced by catalyzing transesterification of vegetable oil with SN5, BN5, and MN5 lipase provided an acid value of 0.8, 1.08, and 0.5 mg/g, viscosity 5.50, 5.7, and 5.53 mm² /s and density 0.87, 0.88, and 0.79 g/ml, respectively. To the best of our knowledge, no such study has been conducted prior on lipase from the seeds mentioned above in Azad Kashmir region.

Screening, purification, and characterization of an extracellular lipase from Aureobasidium pullulans isolated from stuffed buns steamers

An extracellular lipase from Aureobasidium pullulans was obtained and purified with a specific activity of 17.7 U/mg of protein using ultrafiltration and a DEAE-Sepharose Fast Flow column. Characterization of the lipase indicated that it is a novel finding from the species A. pullulans. The molecular weight of the lipase was 39.5 kDa, determined by sodium dodecyl sulfonate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme exhibited its optimum activity at 40 °C and pH of 7. It also showed a remarkable stability in some organic solutions (30%, v/v) including n-propanol, isopropanol, dimethyl sulfoxide (DMSO), and hexane. The catalytic activity of the lipase was enhanced by Ca²⁺ and was slightly inhibited by Mn²⁺ and Zn²⁺ at a concentration of 10 mmol/L. The lipase was activated by the anionic surfactant SDS and the non-ionic surfactants Tween 20, Tween 80, and Triton X-100, but it was drastically inhibited by the cationic surfactant cetyl trimethyl ammonium bromide (CTAB). Furthermore, the lipase was able to hydrolyze a wide variety of edible oils, such as peanut oil, corn oil, sunflower seed oil, sesame oil, and olive oil. Our study indicated that the lipase we obtained is a potential biocatalyst for industrial use.

Optimizing the fermentation conditions and enhanced production of keratinase from Bacillus cereus isolated from halophilic environment

Keratinase degrading Bacillus cereus was isolated from the halophilic environment in Tamilnadu, India and keratinase production was optimized using wheat bran substrate. Of the screened bacterial isolates, four were found to have the ability to produce keratinolytic enzyme. The process parameters were optimized using one-variable-at-a-time approach and response surface methodology. Supplementation of 1% lactose supported more keratinase production (120 U/g). Among the selected nitrogen sources, addition of casein significantly enhanced maximum keratinase production (132.5 U/g). Among the ions, manganese chloride significantly enhanced keratinsase production (102.6 U/g), however addition of zinc sulphate and copper sulphate decreased keratinase production. The maximum keratinase production was obtained in the wheat bran medium containing 1% lactose, 0.5% manganese with 80% moisture (292 U/g). Statistics based contour plots were generated to explore the variations in the response surface and to find the relationship between the keratinase yield and the bioprocess conditions.

Purification and characterization of lipase by Bacillus methylotrophicus PS3 under submerged fermentation and its application in detergent industry

Lipase production bacterial isolate was isolated from soil of service station and identified as Bacillus methylotrophicus PS3 by 16SrRNA with accession number |LN999829.1|. Lipase enzyme was purified by sequential methods of ammonium sulfate precipitation and Sephadex G-100 gel column chromatography. The molecular weight of purified enzyme was 31.40 kDa on SDS-PAGE. This purification procedure resulted in 2.90-fold purification of lipase with a 24.10% final yield. The purified lipase presented maximal hydrolytic activity at a temperature of 55 ^°C, and pH of 7.0. Lipase activity was stimulated by Triton X-100 and SDS with Mg²⁺ and Ca²⁺ metals employ a positive effect and outlast its stable in organic solvent i.e. methanol and ethanol.

Evaluation of biofilm-forming ability of bacterial strains isolated from the roof of an old house

The bacterial diversity associated with biofilm-forming ability was studied. Eighteen bacterial strains were isolated from a microbial film collected from the roof of an old house located in Sfax, Tunisia. The purity of these microorganisms was confirmed by microscopic observation after repeated streaking on a Tryptic Soy agar medium. Biofilm formation was estimated using preliminary tests including a motility test, microbial adhesion to solvents (MATS), and the Congo Red Agar method (CRA). Since these tests showed no significant result, microplate tests, such as crystal violet and resazurin assays, were used. The results obtained showed that strain S61 was able to form a biofilm within 24 h (OD₅₇₀ = 4.87). The viability of the S61 biofilm with resazurin assessed with fluorescence measurement was about 1.5 × 10³. The S61 strain was identified as Staphylococcus epidermidis. In the biofilm studied here, it was the most biofilm-forming bacterium and will be used as a bacterial model for studying anti-biofilm activity.

Diversity Analysis and Bioresource Characterization of Halophilic Bacteria Isolated from a South African Saltpan

Though intensive research has been channeled towards the biotechnological applications of halophiles and other extremophilic microbes, these studies have not been, by any means, exhaustive. Saline environments still offer a vast diversity of microbes with potential to produce an array of natural products which can only be unlocked by concerted research efforts. In this study, a combination of culture and molecular approaches were employed to characterize halophilic bacteria from saltpan water samples and profile their potential biotechnological applications. Physicochemical analysis of the water samples showed that pH was alkaline (pH 8.8), with a salinity of 12.8%. 16S rRNA gene targeted amplicon analysis produced 10 bacterial phyla constituting of Bacteroidetes (30.57%), Proteobacteria (15.27%), Actinobacteria (9.05%), Planctomycetes (5.52%) and Cyanobacteria (3.18%). Eighteen strains were identified using sequencing analysis of the culturable bacterial strains. From these, the strains SP7 and SP9 were positive for cellulase production while the strains SP4, SP8 and SP22 were positive for lipase production. Quantitative enzyme assays showed moderate extracellular cellulase activity (1.95 U/mL) and lipase activity (3.71 U/mL) by the isolate SP9 and SP4 respectively. Further, of the six isolates, the isolate SP9 exhibited exploitable potential in the bioremediation of hydrocarbon pollution as demonstrated by its fairly high activity against benzanthracene (70% DCPIP reduction). Elucidation of the isolates secondary metabolites showed the production of the molecules 2,3-butanediol, hexahydro-3-(2-methylpropyl)pyrrole[1,2a]pyrazine-1,4-dione, aziridine, dimethylamine and ethyl acetate (GC-MS) and oxypurinol and 5-hydroxydecanoic acid (LC-MS), particularly by the isolate Salinivibrio sp. SP9. Overall, the study showed that the isolated halophiles can produce secondary metabolites with potential industrial and pharmaceutical application.

Halophilic Bacteria of Lunsu Produce an Array of Industrially Important Enzymes with Salt Tolerant Activity

The halophilic bacterial isolates SS1, SS2, SS3, SS5, and SS8 were characterized for production of industrially important enzymes like amylase, protease, lipase, and glutaminase. Halophilic bacterial isolates SS1 and SS3 exhibited salt dependent extracellular amylase and protease activities. Both the halophilic isolates SS1 and SS3 exhibited maximum amylase and protease activities in the presence of 1.5 and 1.0 M NaCl, respectively, with the optimum pH 8 and temperature 40°C. SS2 showed maximum extracellular protease and lipase activities in the presence of 0.75 M NaCl, at optimum pH of 7, and temperature 37°C. The glutaminase activity of SS3 increased with increase in concentration of NaCl up to 2.5 M. The optimum pH and temperature for L-glutaminase activity of SS3 was 8 and 40°C, respectively. The combined hydrolytic activities of these halophilic bacterial isolates can be used for bioconversion of organic materials to useful products.

Isolation, identification, and media optimization of high-level cellulase production by Bacillus sp. BCCS A3, in a fermentation system using response surface methodology

Cellulases are important glycosyl hydrolase enzymes, which break down cellulose to β-glucose. They have been used widely in biotechnological processing such as bioethanol production. In this work we studied maximizing cellulase production by Bacillus sp. BCCS A3 using response surface methodology (RSM). A good result was attained with these conditions (% w/v): tryptone 0.1, Na₂PO₄ 0.25, (NH₄)₂SO₄ 0.2, MgSO₄ · 7H₂O 0.005, CaCl₂ 0.005, KH₂PO₄ 0.1, NaCl 0.1, sodium carboxymethylcellulose (CMC) 0.75, and pH 9. The cellulase activity in optimized medium was 49.80 U/ml. Moreover, high level of enzyme production was obtained by using fermentor system (50.30 U/ml). Thus, according to the obtained results, this statistical method provided quick identification and integration of key medium details for Bacillus sp. BCCS A3, leading to more cellulase production.

Halophilic bacteria as a source of novel hydrolytic enzymes

Hydrolases constitute a class of enzymes widely distributed in nature from bacteria to higher eukaryotes. The halotolerance of many enzymes derived from halophilic bacteria can be exploited wherever enzymatic transformations are required to function under physical and chemical conditions, such as in the presence of organic solvents and extremes in temperature and salt content. In recent years, different screening programs have been performed in saline habitats in order to isolate and characterize novel enzymatic activities with different properties to those of conventional enzymes. Several halophilic hydrolases have been described, including amylases, lipases and proteases, and then used for biotechnological applications. Moreover, the discovery of biopolymer-degrading enzymes offers a new solution for the treatment of oilfield waste, where high temperature and salinity are typically found, while providing valuable information about heterotrophic processes in saline environments. In this work, we describe the results obtained in different screening programs specially focused on the diversity of halophiles showing hydrolytic activities in saline and hypersaline habitats, including the description of enzymes with special biochemical properties. The intracellular lipolytic enzyme LipBL, produced by the moderately halophilic bacterium Marinobacter lipolyticus, showed advantages over other lipases, being an enzyme active over a wide range of pH values and temperatures. The immobilized LipBL derivatives obtained and tested in regio- and enantioselective reactions, showed an excellent behavior in the production of free polyunsaturated fatty acids (PUFAs). On the other hand, the extremely halophilic bacterium, Salicola marasensis sp. IC10 showing lipase and protease activities, was studied for its ability to produce promising enzymes in terms of its resistance to temperature and salinity.