Catalysts play a significant role in transesterification of vegetable oils. Currently, chemical and biological catalysts are being investigated, and both have their inherent merits and demerits. In large-scale applications, these catalysts are expected to be cost effective and environmentally friendly. If the catalyst is homogeneous in its physical form it is more effective than is the heterogeneous catalyst, but its separation from the mixture is a major issue. Some of the heterogeneous catalysts suffer leaching in harsh reaction conditions. Of late, nanocatalysts that demonstrate high efficiency are being studed. Nanoparticles are used in biological catalysts as solid carriers for lipase immobilization. Lipase immobilized on magnetic nanoparticles has proved to be a versatile biocatalyst for biodiesel production. This article reviews the role of various catalytic systems commonly used in the transesterification reaction of oils in biodiesel generation.

Free enzymes employed as biological catalysts have many advantages such as low reaction time, involving low energy and less waste output when compared to conventional chemical catalysts. However, commercial utilization of free enzymes is often hampered by the lack of operational stability, high cost, and non‐reusability. Immobilization of enzyme is an option to overcome these obstacles. Immobilized enzyme expresses stable performance in organic solvents even in adverse pH, which makes the biomolecules reusable and prosperous as a biological catalyst. Biological catalysis with immobilized enzymes is found to be an alternative method instead of chemical catalysis for chemical reactions in the foreseeable future. Sources of lipase, techniques in immobilization and cross‐linkers are dealt with in this paper.

The recent developments made regarding the novel, cost-effective, and environmentally friendly nanocatalysts for the electrochemical sensing of biomolecules, pesticides, nitro compounds and heavy metal ions are discussed in this review article.

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Carriers used in the immobilization process play a major role in enhancing the properties of the biocatalyst. Polymers are used as organic carriers for enzyme immobilization to improve the thermal, chemical, and operational stability of the enzyme. A variety of carriers are used in the immobilization of enzymes, e.g., mica, silica, zeolites, hydrotalcites, activated carbon, gold and magnetic nanoparticles. Silica‐based carriers offer suitable matrices for enzyme immobilization to manufacture industrial products. Immobilization on nanoparticles has become attractive in biocatalytic applications due to the combination of physical, chemical, catalytic, electronic, and optical properties. Gold nanoparticles also have received attention in the preparation of biocatalysts due to the above‐mentioned reasons. Magnetic nanoparticles are used as a carrier since they can be isolated by an external magnetic field, which is of special interest in the synthesis of organic products such as biodiesel. Different carrier materials involved in the immobilization of enzymes are discussed in this paper.