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Lipases can be obtained from plants, animals, and microorganisms and based on that lipases can be classified on it as plant, animal, and microbial lipases depending on their origin respectively. Lipases from different sources with different structure has different properties and catalytic activities. We can use this to counter lipase problems in biodiesel production like lipase cost and methanol inhibition. We need to optimize reaction conditions according to chosen substrate and lipase from specific source [107]. Microbial lipases are widely used at industrial and commercial level as biocatalysts for biodiesel production because microbial lipases are more stable and can be produced in bulk amount from microorganism [23]. Microbial lipases can be manipulated genetically with ease, seasonal changes have nothing to do with lipase production, and rapid growth of microbes makes them the ideal candidates as lipase source [120, 121]. Use of microbial lipase is increasing day after day and currently 5% of the world enzyme market is being shared with microbial lipases [121]. Microbial lipase weighs around 30–50 kDa and their optimum pH to work at is 7.5. Based on temperature tolerance, microbial lipases can be categorized as mesophilic and thermophilic lipases. Mesophilic lipases normally work at 35°C–50°C and they become denature above 70°C while thermophilic or thermostable lipases normally work at 60°C–80°C, but some also work at 100°C under specific conditions [122, 123]. According to Hotta et al. [123], lipases from Pyrobaculum calidifonti (hyperthermophilic archae) showed its activity at 90°C. Similarly, thermostable lipases from Caldanaerobacter subterraneus and Thermoanaerobacter thermohydrosulfuricus (highly thermophilic bacteria) performed well in the range of 40°C–90°C. They not only performed well at high temperatures but also were resistant toward organics solvents [124]. Lipase producing microorganisms can be isolated from soil, waste water, marine water, and industrial wastes. Isolates of Mucor, Sclerotina, Candida, and Aspergillus strains have been reported, which were isolated from soil. Similarly, various strains of microbes such as P. alcaligenes, Bacillus acidophilus, Enterobacter intermedium, P. fluorescens, and Geotrichum asteroids are also reported as lipase producing strains when isolated from vegetable oil processing plants [141]. Screening of microbes is done by checking their lipolytic. Generally, lipases are screened using batch cultures having agar as substrate but this is time consuming. So, the two mostly used methods for lipase production are solid state fermentation and using submerged culture [142]. Purified form of lipases is used in biochemical reaction to get maximum benefit from it, so purification is required. Purification of lipase requires several techniques including ammonium sulfate precipitation or ultrafiltration and after that more sensitive and advanced techniques are utilized like gel filtration, ion exchange chromatography, and affinity chromatography [143]. Moreover, some other novel techniques can also be applied to purify lipases such as immunopurification, column chromatography, hydrophobic interaction chromatography, and membrane process. Generally, the strategy used for purification lipases starts with the removal of lipase producing cells from their growth culture to get extracellular lipases after fermentation. Then, the extract without cells is concentrated by organic solvents, ultrafiltration, and precipitation using ammonium sulfate. Ammonium sulfate precipitation is used in the first stages of purification and it crudely separate out things from mixture. After that advanced techniques of chromatography are used to finely purify lipases [144]. According to Javed et al. [112], diverse data from various research work suggested that purification had been done from 2.4 to 500 folds with an increase in yield from 10.3% to 36%. Effective production and purification strategies of lipases are being designed to get maximum yield at a very small expense. Among microbial lipases, the most commonly used lipase sources are bacteria, fungi, yeast, and algae; see Table 1.1 for some bacterial lipases and Table 1.2. for fungal lipases that are used for biodiesel production [46]. Some of the commercially available enzymes for biodiesel production are enlisted in Table 1.3.