**3. Conclusion**

*Molecular Biotechnology*

(99.9%) and was stable in 70% organic solvent and temperature of 45°C [24]. The biocatalytic method was advantageous in the sense that it omitted the use of hazardous chemical catalyst chlorodiisopinocampheylborane (DIP-CI), which was conventionally used. Several other drugs such as atorvastatin, crizotinib, duloxetine, and phenylephrine were also developed by biocatalytic

• Atorvastatin—It comes from the statin family and is marketed under the trade name Lipitor by Pfizer. This drug reduces cholesterol levels by inhibiting the synthesis of cholesterol in the liver [42]. Atorvastatin production is also carried out by employing KRED for the production of hydroxy nitrile, an important intermediate. It is a multienzyme process involving glucose dehydrogenase (GDH), KRED, and halohydrindehalogenase (HHDH). Thus, the process is

• Pregabalin—Pregabalin, a lipophilic GABA (*γ*-aminobutyric acid) analog, finds use in the treatment of various central nervous system ailments including neuropathic pain, fibromyalgia, epilepsy, and anxiety [43, 44]. Its production was carried out by biocatalytic conversion of *rac*-2-carboxyethyl-3-cyano-5-methylhexanoic acid ethyl ester to 2-carboxyethyl-3-cyano-5-methylhexanoic acid using lipolase. A heat-promoted decarboxylation of 2-carboxyethyl-3-cyano-5-methylhexanoic acid yielded (*S*)-3-cyano-5-methylhexanoic acid ethyl ester, which is a principal known precursor of pregabalin [45]. The mentioned chemoenzymatic synthesis route not only produced increased yields of pregabalin (40–45%) but also eliminated wastes and usage of organic solvent.

• 7-ACA (7-aminocephalosporic acid)—Cephalosporin has been extensively used as semisynthetic antibiotics; it acts on bacterial cell wall (peptidoglycan) synthesis. 7-Aminocephalosporanic acid (7-ACA), the critical intermediate or precursor for the production cephalosporins, is biocatalytically produced by

Lipase B *Candida antarctica* Reboxetine [49]

Oxidase *P. simplicissimum* Pinoresinol [51]

**compounds**

Carbovir, abacavir, melogliptin

(active ingredient of AZILECT®)

Simvastatin [52, 53]

*Yarrowia lipolytica* Statins [50]

— Armodafinil [54]

*Erwinia herbicola* cells l-DOPA [57]

*Caldicellulosiruptor saccharolyticus* Lactulose [58]

**References**

[5, 55]

[56]

**Biocatalysts Microbial sources Pharmaceutical** 

overexpressing LovD

Immobilized lipase *Thermomyces lanuginosus* Rasagiline mesylate

*List of biocatalysts and their microbial source employed for the synthesis of pharmaceutical drugs.*

Acyltransferase (LovD) Whole-cell *Escherichia coli* strain

(+)-γ-lactamases *Bradyrhizobium japonicum*

USDA 6

process using KRED from bacterium *Lactobacillus kefir* [29].

environmentally as well as economically feasible.

**26**

**Table 2.**

Carbonyl reductase

Expressing tyrosine phenollyase

*E. coli* cells expressing cellobiose 2-epimerase

(YlCR2)

Engineered cyclohexanone monooxygenase

Biocatalysis has made a remarkable journey so far and has been successfully applied for the numerous biotransformation processes in several industries. It has benefitted nearly all sectors, particularly chemical and pharmaceuticals. The flourishing development of economically viable and sustainable chemoenzymatic processes highly depends on the broader availability and applicability of enzymes with robust performance irrespective of extreme conditions. Recent surveys have shown that most of the biocatalysts are being used in the synthesis of pharmaceuticals or drugs or intermediates replacing some of the chemical processes, but their stability, selectivity, and specificity are of prime concern.
