Degradation Medium Conditions

Taken from Tsuji, with permission from John Wiley Sons, Inc. 

L-lactic acid oligomers esterified with N-(2-hydro g ropyl) methacrylate and showed that the hydrolytic degradation of hydro g -terminated L-lactic acid oligomers seemed to proceed via a hack-hiting cleavage, which resulted in dimer formation, whereas that of acetylated L-lactic acid oligomers took place via random chain cleavage. 

Acidic media can also accelerate the hydrolytic degradation of PLA-based materials. However, when the molecular weight of PLA is higher than 1x10 g moP, hydronium ions seem to have an insignificant or a veiy low catalytic effect on the hydrolytic degradation of PLA-based materials.  

Molecular weight is one of the most crucial factors for the hydrolytic degradation rate of PLA-based materials. Saha et studied the effect of 

Numata et reported that 22 branches of polyglycerine eo-initiated PDLLA enhanced the alkaline hydrolytic degradation of the polymer matrix. They also found that six branches of myo-inositol-co-initiated PDLLA had no effect on the alkaline hydrolytic degradation of PLLA, according to gel permeation chromatography results. 

---

Higher temperatures result in permanent degradation. The amount of this irreversible loss in mechanical properties depends upon moisture content, heating medium, temperature, exposure period, and, to some extent, species. The effects of these factors on modulus of mpture, modulus of elasticity, and work to maximum load are illustrated in Figures 6—9 (6). The effects may be less severe for commercial lumber than for clear wood heated in air (Fig. 10). The permanent property losses shown are based on tests conducted after specimens were cooled to - 24° C and conditioned to a moisture content of... 

Trifluoroacetic acid is a useful medium for a number of oxidation reactions It IS highly resistant to strong oxidants, even to permanganates and chromates For instance, various alkanes, cycloalkanes, and arenes can be oxidized degradatively by potassium permanganate in trifluoroacetic acid under mild conditions [28]... 

The growth medium for a bioprocess should ideally provide all the requirements of the process organism in such a way that the organism grows rapidly, produces large amount of the desired product, does not degrade the final product, and is able to survive under harsh environmental conditions (such as shear forces, oxygen limitation etc). 

Degradation of bixin dissolved in a water medium with 0.2% Tween 80 followed first-order rate, either in the dark or under fluorescent light (700 lux), both at 21°C. As expected, degradation was much higher under light (ko, s = 3.79 x KTVmin) than in dark conditions = 7.25 x lO Vmin). ... 

Kanasawud and Crouzet have studied the mechanism for formation of volatile compounds by thermal degradation of p-carotene and lycopene in aqueous medium (Kanasawud and Crouzet 1990a,b). Such a model system is considered by the authors to be representative of the conditions found during the treatment of vegetable products. In the case of lycopene, two of the compounds identified, 2-methyl-2-hepten-6-one and citral, have already been found in the volatile fraction of tomato and tomato products. New compounds have been identified 5-hexen-2-one, hexane-2,5-dione, and 6-methyl-3,5-heptadien-2-one, possibly formed from transient pseudoionone and geranyl acetate. According to the kinetics of their formation, the authors concluded that most of these products are formed mainly from all-(E) -lycopene and not (Z)-isomers of lycopene, which are also found as minor products in the reaction mixture. 

---