Ethephon [Ethrel, (2-chloroethyl) phosphonic acid, 2-CEPA] was tested on ‘Hamlin’ oranges in 2 seasons and on ‘Valencia’ oranges and ‘Marsh’ grapefruit in 1. In 1 picking, very green oranges, mature enough to degreen with gaseous ethylene (C2H4), failed to degreen with ethephon. Once mature enough to respond to ethephon, rate of chlorophyll disappearance was comparable to C2H4 degreening. Waxing sharply arrested color change due to C2H4 degreening, but had comparatively little effect on ethephon-dipped fruit. Stem feeding was effective but impractical. Little correlation was found between degreening rate and: ethephon concn (from 1,000 to 12,000 ppm); immersion time (from 1 to 10 min); or use of vacuum vs. atmospheric pressure during immersion. Duration of color change was sometimes sharply curtailed after brief immersion periods or low ethephon concn. Internal C2H4 levels increased from 0 prior to ethephon treatment to 5-16 ppm 24 hr after, with emanation rates from the fruit of 1 to 6 µl/Kg/hr. It is theorized that a threshold concn is necessary for degreening with no indication of stimulation of autogenous C2H4 production.
Fouling induced enzyme immobilization on polymer membrane with controlled variables can retain enzyme stability and performance. In this study, the effect of enzyme concentration towards the fouling-induced enzyme immobilization was investigated. Alcohol dehydrogenase (ADH) was used as model enzyme to be immobilized on poly(ether) sulfone (PES) membrane at different concentration (0.05, 0.10 and 0.20 g/L). The transmembrane pressure and pH were fixed at 2 bar and pH 7 respectively during the process takes place. The result shows that higher enzyme concentration gives higher loading efficiency with 83.95%. Hermia’s model predicted that standard and intermediate blocking dominating the fouling mechanism at all enzyme concentration tested.
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