Microbial Enzymes Associated with Fresh-cut Produce

Preparation and handling procedures for fresh-cut mango slices were developed using `Tommy Atkins', `Haden', and `Palmer' mangoes. Fruit with yellow flesh color (no green color remaining) were optimum maturity for fresh-cut in terms of maintenance of acceptable appearance, texture, and taste; riper fruit developed flesh breakdown and more browning. Postharvest life of fresh-cut mango at 5 °C was 8 to 10 d with no evidence of chilling injury and was limited by flesh browning and loss of firmness. Respiration rates ranged from 32 to 40 mg CO2/kg per hr and ethylene production was typically ≤0.1 μl·kg–1·hr–1. The SSC changed little during storage, while pH varied from 3.5 to 4.8 and TA typically declined by 30% to 40%. Peeling to a depth of at least 2 mm and trimming flesh near the stem scar was necessary to minimize browning. Imported fruit that had been heat-treated for insect quarantine showed more severe browning than Florida fruit that had not been heat-treated. Preparation in aseptic conditions and dipping fruit in a 100 ppm NaOCl solution at pH 7 before and after peeling protected against decay during storage but dipping in chlorine after slicing without removal of excess liquid resulted in flesh translucency and breakdown. Dipping in 1% CaCl2 solution had no effect on flesh firmness (Instron) or browning. Storage in an unvented plastic clamshell container, which developed an atmosphere of 2.25% CO2 plus 19% O2, did not improve shelf life, but a MA of 10% CO2 plus 10% O2 was subjectively judged to slow browning and softening and resulted in no off flavor compared to air storage.

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Microbial enzymes used in prodrug activation for cancer therapy: Insights and future perspectives

Current Protein and Peptide Science ◽

10.2174/1389203721666201207231932 ◽

2020 ◽

Vol 21 ◽

Author(s):

Rakhi Dhankhar ◽

Anubhuti Kawatra ◽

Aparajita Mohanty ◽

Pooja Gulati

Keyword(s):

Purine Nucleoside Phosphorylase ◽

Cytosine Deaminase ◽

Therapeutic Index ◽

Enzyme Prodrug Therapy ◽

Prodrug Activation ◽

Microbial Enzymes ◽

High Productivity ◽

Delivery Vector ◽

Exogenous Enzymes ◽

Activation Therapy

Abstract:: Enzyme prodrug therapy has gained momentum in the recent years due to their ability to improve therapeutic index (benefits versus toxic side-effects) and efficacy of chemotherapy in cancer treatment. Inactive prodrugs used in this system are converted into active anti-cancerous drugs by enzymes, specifically within the tumor cells. This therapy involves three components namely prodrug, enzyme and gene delivery vector. Past reports have clearly indicated that the choice of enzyme used, is the major determinant for the success of this therapy. Generally, enzymes from non-human sources are employed to avoid off-target toxicity. Exogenous enzymes also give a better control to the clinician regarding the calibration of treatment by site-specific initiation. Amongst these exo-enzymes, microbial enzymes are preferred due to their high productivity, stability and ease of manipulation. The present review focuses on the commonly used microbial enzymes particularly cytosine deaminase, nitroreductase, carboxypeptidase, purine nucleoside phosphorylase in prodrug activation therapy. Various aspects viz. source of the enzymes, types of cancer targeted, mode of action and efficacy of the enzyme/prodrug system, efficient vectors used and recent research developments of each of these enzymes are comprehensively elaborated. Further, the results of the clinical trials and various strategies to improve their clinical applicability are also discussed.

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