Studies on Limonin Biotransformat Ion by Pseudomonas Putida

Abstract

Kinnow, which is the hybrid of Citrus nobilis and Citrus delicosa, was developed through lengthy hybridization process. The main problem in acceptability of Kinnow fruit juice is the development of bitterness with time. Two principle components responsible for the development of bitterness in Kinnow juice are naringin (immediate bitterness) and limonin (delayed bitterness). Several efforts have been made abroad to process citrus juice that is free from bitterness. Though all these methods showed certain results, considerable success has not been found in debittering technology. Further, most of the research has been restricted to grapefruit juice and other citrus fruit juices. Very little work has been done on Kinnow fruit juice. The present work aimed to address this problem using Pseudomonas putida. Firstly, optimum growth conditions for Pseudomonas putida were studied where in different parameters like pH, temperature, duration, source of limonin, and type of growth medium were optimized for maximum limonin biotransformation. Further, an attempt was made to identify the reaction products so formed. Maximum limonin biotransformation along with optimum growth could be achieved by growing Pseudomonas putida at a temperature of 35oC and pH 5 for 120 hours. Results of thin layer chromatography indicated the presence of deoxylimonin and deoxylimonoic acid in the culture medium. Future work needs to be done to confirm the metabolites of limonin as well as to purify and characterize the bacterial enzymes involved in the pathway.