Faculty Publications
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Item Production, Purification and Characterization of Extracellular Tannase from a Newly Isolated Yeast, Geotrichum cucujoidarum(Journal of Pure and Applied Microbiology, 2022) Thangavelu, N.; Hugar, P.; Belur, P.D.With an aim to isolate a tannase positive organism, the microbial mat growing on the stored areca extract leachate surface was screened. Once the tannase positive organism was isolated, it was identified by ITS/18S rRNA gene sequencing. Further, the enzyme was purified and examined for its biochemical properties. A potent extracellular tannase-producing yeast was isolated and was identified as Geotrichum cucujoidarum. After the shake flask studies, the enzyme activity of 4.42 U/ml and specific activity of 29.86 U/mg were achieved in a medium with tannic acid as an inducer. Later, ethanol (70%) precipitation followed by purification through FPLC using SEC 650 column resulted in 166.37 U/mg specific activity and a recovery of 50.54%. The purified enzyme was a monomer with a molecular weight of 63 kDa. The optimum pH and the temperature of the enzyme were found to be 5.0 and 30°C, respectively. The Michaelis-Menten constant (Km) was found to be 2.9 mM, and the turn over number (kcat) and catalytic efficiency (kcat/km) of the purified tannase were 102 S-1 and 35.17 mM-1S-1 respectively. Temperature and pH stability profiles of the enzyme, influence of various metal ions, chelators and surfactants on enzyme activity and kinetic constants of enzyme shows that the tannase produced from Geotrichum cucujoidarum is unique and is a potential candidate for further studies. © The Author(s) 2022.Item Fermentative extraction of phenolic compounds from unripe areca nuts by solid-state fermentation using newly isolated Rhizopus orizae MW538932(John Wiley and Sons Inc, 2023) Hugar, P.; Belur, P.D.; Raval, K.Areca nut (pericarp of Areca catechu L.) is a rich source of valuable phenolic compounds. Presence of a psychoactive agent, Arecoline, pose a challenge in the use of areca nut extracts. With an aim to maximise the extraction of phenolic compounds, a newly isolated Rhizopus orizae MW538932, was employed for the solid-state fermentation of unripe areca nut (6–7 months' maturity) powder. Supplementary nutrients (carbon and nitrogen sources) for the media and the solvents for the extraction of phenolic compounds from the fermented medium were optimised. The optimised process could produce an extract having a total phenolic content of 186.03 ± 2.50 mg gallic acid equivalent and total flavonoid content of 139.70 ± 2.00 mg catechin equivalent per gram of the sample. UHPLC–MS/MS studies and HPLC analysis showed the presence of plethora of phenolic compounds and the absence of Arecoline and other alkaloids. This flavonoid-rich extract can be a potential source of natural antioxidants for food and pharmaceutical industry. © 2023 Institute of Food, Science and Technology (IFSTTF).Item Phenolic profile of unripe areca nuts cultivated in various districts of Karnataka, India(John Wiley and Sons Ltd, 2024) Hugar, P.; Dutta, A.; Srilakshmi, S.; Belur, P.D.; Raval, K.; Iyyaswami, R.Background: Annual production of areca nut in Karnataka state exceeds 1.08 million tonnes, contributing 80% and 49% to Indian and global production, respectively. Areca nut (pericarp of Areca catechu L.) is found to be a rich source of valuable phenolic compounds. Total phenolic content (TPC) and total flavonoid content (TFC) were estimated in 21 unripe areca nut samples collected from the major areca nut growing regions of Karnataka state. Arecoline, a prominent alkaloid present in areca nut was estimated and phenolic profile of one areca nut sample was generated using UHPLC–MS/MS studies. Results: A significant variability was found in TPC, TFC and arecoline content among the samples, belongs to different agroclimatic zones. Flavonoids were found to be the major phenolic compounds present in these unripe areca nut samples. The median values of TPC, TFC and arecoline were found to be 99.609 ± 0.002 mg gallic acid equivalent, 78.86 ± 0.007 mg catechin equivalent and 2.17 ± 0.13 mg/g of the sample on fresh weight basis. A positive correlation was found to exist between TPC and arecoline content in the green unripe areca nuts of 6–7 months' maturity. Through UHPLC–MS/MS studies, 61 prominent compounds have been identified. Conclusion: The TPC and TFC of areca nuts collected from different districts of Karnataka falling in various agroclimatic zones varied significantly. In general, the arecoline content found in all these samples was less than that reported elsewhere, and the variability among the samples was also found to be minimal. A positive correlation was observed between TPC and arecoline. UHPLC–MS/MS studies showed the presence of about 52 unique phenolic compounds. © 2023 The Authors. JSFA Reports published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.