Stable esterase obtained from palmarosa

Abstract

A novel esterase, cleaving acyclic monoterpenyl esters into their monoterpenols, has been detected in the crude enzymic preparation of palmarosa ( Cymbopogon martinii ) inflorescence. The extraction and assay condition for the enzyme has been standardized. The esterase enzyme has shown maximum activity in the alkaline pH range, with optimum temperature at 30° C. using geranyl acetate (acyclic monoterpenyl acetate) as substrate. Time course hydrolysis of geranyl acetate using crude enzymic preparation revealed that after 24 hours of incubation approximately 75% geranyl acetate was hydrolyzed. The crude esterase enzyme, when stored at 4° C., was quite stable for one week with 40% loss of activity. The enzyme also has the capability to hydrolyze other acyclic monoterpenyl esters such as geranyl formate and citronellyl acetate, which are normally present in several aromatic plant species.

We claim:  
     
         1 . A stable esterase obtained extracted from plant tissues of a natural plant source.  
     
     
         2 . A stable esterase as claimed in  claim 1  wherein the natural source is selected from plant tissues of palmarosa, lemon grass and other aromatic plants.  
     
     
         3 . A stable esterase as claimed in  claim 2  wherein the plant tissues are selected from inflorescence of palmarosa, leaf tissues of lemongrass and other aromatic plants.  
     
     
         4 . A stable esterase of  claim 1  wherein the esterase is stable when stored at 4° C. for one week.  
     
     
         5 . A stable esterase as claimed in  claim 3  wherein the esterase is highly active in the alkaline pH range between 8.0-9.0 and temperature range between 20-40° C.  
     
     
         6 . A esterase as claimed in  claim 5  wherein optimum activity is found at pH 8.5 and temperature 30° C.  
     
     
         7 . A esterase as claimed in  claim 1  having a linear catalytic rate of up to six hours of incubation at 30° C.  
     
     
         8 . A esterase as claimed in  claim 1  being a site specific monoterpenyl ester hydrolase capable of removing the terminal ester group of acyclic monoterpenyl esters, thereby producing monoterpenyl alcohols.  
     
     
         9 . A process for the extraction of a stable esterase from plant tissues from a natural source and useful for the cleaving of acyclic monoterpenyl esters into their corresponding alcohols, said process comprising; homogenizing the plant tissue in a cold extraction medium (1 g tissue/3 ml) consisting of 0.1 M buffer (pH 6.5) containing 50 mM sodium metabisulphite, 10 mM β-mercaptoethanol, 10 mM ascrobic acid, 0.25 M sucrose and 1 mM EDTA-Na 2 , squeezing the slurry through four layius of muslin cloth, centrifuging at 15, 000× g for 60-80 minute, adding purified amberlite XAD-4 resin to the supernatant (half of the tissue weight), keeping it for 4-6 minutes at 4° C. filtering the slurry thus obtained through muslin cloth to get a clear supernatant, which is used as a esterase enzyme source.  
     
     
         10 . A process as claimed in  claim 9 , wherein plant tissues from a natural source are selected from inflorescence of palmarosa, leaf tissues of lemongrass and some other aromatic plants.  
     
     
         11 . A process as claimed in  claim 9  wherein the buffer is selected fom NaPi and Tris-HCl.  
     
     
         12 . A process for hydrolysis of the oil containing the mixture of acyclic monoterpenyl esters into their corresponding alcohols by using a novel esterase of  claim 1 .  
     
     
         13 . A process as claimed in  claim 12  wherein the acyclic monoterpenyl esters are selected from geranyl acetate, geranyl formate and citronellyl acetate.  
     
     
         14 . A process as claimed in  claim 13  wherein 75% of the geranyl acetate was hydrolyzed to its corresponding alcohol after 24 hours of incubation.  
     
     
         15 . A process as claimed in  claim 14  wherein the terminal group of the acyclic monoterpenyl esters is removed to obtain the corresponding monoterpenyl alcohols.