Gallic acid is a phenolic compound ubiquitous in every part of the plant. It is quite high in Melissa officinalis plants and also known as lemon balm that belongs to Lamiaceae family. It is a short rooted and spreading herb which has anti-inflammatory, psychoneurological, antispasmolytic, antifungal, antiviral, antiparasitic and antioxidant activities. Medicinal drugs made from these leaves and plants have a faint lemon aroma that contains several phytochemicals and pharmacological properties making this herb an ideal for body and skin care use. Our aim is to, enhance gallic acid from the leaves of Melissa officinalis by Bacillus substilis through submerged fermentation. Our research showed that there is an increase of gallic acid upto 17.0 µg/ml during bio-transformation processes and bioanalytical techniques where conversion of tannic acid to gallic acid is triggered by tannase enzyme produced by Bacillus substilis. It was extracted from solvent extraction method from this plant and estimated by Folin–Ciocalteus reagent and was used in fermentation process for enhancement of gallic acid. The gallic acid concentration was increased and found to be 17.0µg/ml. Especially the gallic acid is enhanced due the activity of tannase enzyme which may converts tannic acid to gallic acid. This enzyme was produced by Bacillus substilis which acts as biocatalyst and converts tannic acid to gallic acid. Thus, this microorganism is essential for the biotransformation of tannic acid to gallic acid. In this research work, biotransformation has played a vital role for gallic acid enhancement. Glucose solution is consumed by Bacillus substilis. Here glucose is estimated by DNS reagent (3,5-Dinitrosalicylic acid) and tannic acid estimated by FD reagent (Folin – Denis reagent). Based on various time intervals, the concentration of gallic acid, enzyme concentration and biomass were increased but the tannic acid and glucose concentrations were decreased.