Saby John

Biotechnology, Ecology, Evolutionary Biology



  • K. Saby John · S. G. Bhat · U. J. S. Prasada Rao
    [Show abstract] [Hide abstract]
    ABSTRACT: Mango sap (latex), a by-product in mango industry, was separated into upper non-aqueous phase and lower aqueous phase. Aqueous phase contains very low protein (4.3mg/ml) but contains high specific activities for peroxidase and polyphenol oxidase. The aqueous phase of sap was subjected to ion-exchange chromatography on DEAE-Sephacel. The bound protein was separated into three enzyme peaks: peak I showed peroxidase activity, peak II showed polyphenol oxidase activity and peak III showed activities against substrates of peroxidase as well as polyphenol oxidase. On native PAGE and SDS-PAGE, each peak showed a single band. Based on the substrate specificity and inhibitor studies peak III was identified as laccase. Although they showed variations in their mobility on native PAGE, these enzymes showed similar molecular weight of 100,000±5000. These enzymes exhibited maximum activity at pH 6 however, polyphenol oxidase showed good activity even in basic pH. Peroxidase and polyphenol oxidase showed stability up to 70°C while laccase was found to be stable up to 60°C. Syringaldazine was the best substrate for laccase while catechol was the best for polyphenol oxidase. Thus, mango sap a by-product in mango industry is a good source of these phenol oxidases.
    No preview · Article · Jan 2011 · Journal of Molecular Catalysis B Enzymatic
    [Show abstract] [Hide abstract]
    ABSTRACT: Sap (latex) that oozes out from mango during harvest, upon contact with the fruit, causes dark spots (sap-injury) on the peel and reduces consumer acceptance and shelf-life of fruit. In this investigation different components responsible for sap-injury were identified. Mango saps from four Indian varieties were collected and separated into aqueous and nonaqueous phases. Whole sap, aqueous phase and nonaqueous phase were tested for their ability to cause sap-injury (browning) on mangoes. The nonaqueous phase caused maximum injury and the extent of injury caused by nonaqueous phases from different varieties was varied. Limonene, ocimene and β-myrcene, the major terpenoids identified in saps of Indian varieties, caused injury. Similar type of injury on mangoes was also caused by organic solvents. Damage on Totapuri mango fruit was significantly lower compared to other varieties, whereas Totapuri nonaqueous phase caused injury on all other varieties. The peel of Totapuri variety had very low level of polyphenol oxidase, peroxidase and polyphenols compared to other varieties. Thus, a clear relation was found between the peel polyphenol oxidase, peroxidase activities, the polyphenol content in the peel and the extent of injury. Further, nonaqueous phase applied on peels previously heat-treated at 95C for 5 min, neither caused injury nor showed any enzyme activity. Thus, the results indicated that the terpenoid components of sap and polyphenol oxidase, peroxidase, polyphenols of peel are involved in sap-injury.
    No preview · Article · Feb 2007 · Journal of Food Biochemistry
  • K Saby John · S.G. Bhat · U.J.S. Prasada Rao
    [Show abstract] [Hide abstract]
    ABSTRACT: Mango sap (latex) from four Indian varieties was studied for its composition. Sap was separated into non-aqueous and aqueous phases. Earlier, we reported that the non-aqueous phase contained mainly mono-terpenes having raw mango aroma (Phytochemistry 52 (1999) 891). In the present study biochemical composition of the aqueous phase was studied. Aqueous phase contained little amount of protein (2.0-3.5 mg/ml) but showed high polyphenol oxidase (147-214 U/mg protein) and peroxidase (401-561 U/mg protein) activities. It contained low amounts of polyphenols and protease activities. On native PAGE, all the major protein bands exhibited both polyphenol oxidase and peroxidase activities. Both polyphenol oxidase and peroxidase activities were found to be stable in the aqueous phase of sap at 4 degrees C. Sap contained large amount of non-dialyzable and non-starchy carbohydrate (260-343 mg/ml sap) which may be responsible for maintaining a considerable pressure of fluid in the ducts. Thus, the mango sap could be a valuable by-product in the mango industry as it contains some of the valuable enzymes and aroma components.
    No preview · Article · Feb 2003 · Phytochemistry
  •  K. Saby John · S.G. Bhat · U.J.S. Prasada Rao

    No preview · Article · Jan 2003 · Phytochemistry
  • PS Negi · Saby K. John · Prasada U. Rao
    [Show abstract] [Hide abstract]
    ABSTRACT: Mango is an important tropical fruit. During harvesting of the fruit, sap oozes out at the abscission zone, which is separable into an aqueous phase (AP) and a non-aqueous phase (NAP). The sap from different Indian mango varieties was tested against different fungi and bacteria to evaluate its anti-microbial activity. Fusarium moniliforme was found to be the most resistant and Penicillium spp. the most sensitive to the NAP of sap. Likewise, the NAP of sap was least effective against Escherichia coli while Bacillus cereus was most sensitive to it. The AP of sap did not show antimicrobial activity even at higher concentrations. The most effective anti-fungal activity was exhibited by mango sap from the Mallika variety, whereas sap from different varieties showed variable anti-bacterial activity. Mango sap has a typical raw mango aroma. This combined with its anti-microbial properties may make it suitable for use as a preservative and a flavoring agent in food.
    No preview · Article · Mar 2002 · European Food Research and Technology
  •  K. Saby John · S.G. Bhat · U.J.S. Prasada Rao

    No preview · Article · Jan 2002 · Journal of Food Biochemistry
  •  K.P.S. Negi · K. Saby John · U.J.S. Prasada Rao

    No preview · Article · Jan 2002 · European Food Research and Technology
  •  K. Saby John · L. Jagan Mohan Rao · S.G. Bhat · U.J.S. Prasada Rao
    [Show abstract] [Hide abstract]
    ABSTRACT: Saps (latex) from seven Indian mango varieties were collected immediately after destalking the mature fruit. The amount of sap so collected varied from variety to variety. Sap was separable into two phases, aqueous and nonaqueous, and their ratio was different for each variety. GC-MS analysis of the nonaqueous phase of saps revealed that they mainly consisted of mono-terpenes viz, β-myrcene, trans-/cis-ocimene and limonene being major. There were however, differences in the composition and concentrations of these terpenoid compounds.
    No preview · Article · Nov 1999 · Phytochemistry

4 Following View all

12 Followers View all