Pectin/enzyme ratio

Fig. 10 Chlorpheniramine maleate (CPM) release as a function of the pectin/enzyme ratio within the plug. (From Ref. l)...

Enzymatic degradation of pectin can be satisfactory performed in UF-membrane reactors which have been proved to be helpful tool for laboratory scale investigations. Reaction products can be continuously recovered in a sequence of filtration stages. The obtained product distribution depends on the enzyme to substrate ratio, which affects particularly the... 

Each fruit has specific quantities and ratio of pectin, hemicelluloses and cellulose. These polysaccharides are important concerning enzymes activities required to produce juices and concentrates. Moreover, even if molecular weight and methylation degree of the pectin are specific for each fruit, during the fruit maturation, endogenous pectinases depolymerases and esterase are changing the pectin characteristics This broad variability of raw material makes difficult the standardisation of fruits processing. 

When Rhizopus sp. 26R was cultivated in the solid substrates without addition of rice bran but composed of only wheat bran and rice husk at the ratio of 18 2. The pectinase activity from the culture was approx. 25-35 unit/ml within 2 days and the production remained constant for 4 days (Figure 3). One gram of raw starch from cassava tuber, 1 g of pectin or 0.5 g of yeast extract was added to the solid substrates in order to induce higher activity of the enzsrme. The results showed that either 1 g raw cassava starch or 1 g pectin that was added to the 20 g solid substrates increased the enzyme activity to 1.7 and 2.4 times, respectively (Figure 3). The production of pectinase in soHd substrates with wheat bran and rice husk could be enhanced with the addition of raw cassava starch and pectin. 

Addition of rice bran to the solid substrates to make the ratio of wheat bran, rice bran and rice husk to 9 9 2 helped increasing the activity of pectinases from Rhizopus sp. 26R as shown in Figure 4. The activity of the enzyme was approx. 4.3 times higher. Moreover, either 1 g of pectin or 0.5 g of yeast extract did not help increasing of the enzyme production. In contrary, the enz5mie activity was decreased 2.6 times to that of the former one. Addition of raw cassava starch to the substrates did no effect to the enzyme production (data not shown). 

Addition of rice bran to the mixture of wheat bran and rice husk was the best substrates for the fungal pectinase production. The solid substrates that composed of wheat bran, rice bran and rice husk at the ratio of 6 12 2 was selected to be the best since rice bran are easily found in South-east Asian countries. Addition of either raw cassava starch or pectin as inducer is not needed. On the otherhand, pectin even inhibited the activity of the enzyme as well as that reported by Elegado and Fujio (6). 

A practical technique for lactic acid fermentation of potato pulp has been developed (Oda et al., 2002). They screened 38 strains of the fungus Rhizopus oryzae either lactic acid or fumaric acid and ethanol were formed, and the ratio differed among the strains tested. Saito et al. (2003) studied the effect of pectinolytic enzymes on lactic acid fermentation of potato pulp by different Rhizopus oryzae NRRL 395 and NBRC 4707 strains. When a commercial preparation of pectinase was added to potato pulp inoculated with fungal spores and incubated for 7 days, both strains effectively produced larger amounts of lactic acid and ethanol. These data indicated that the fermentation of potato pulp depends on the degradation of pectic substances in NRRL 395 and NBRC 4707. Saito et al. (2006) evaluated the potato pulp obtained in different seasons and found pectin content to be dependent on the dates of extraction. 

Plug degradation could also be achieved by enzymes being directly incorporated into the plug. In an example, plugs containing pectin, a natural polysaccharide, were degraded by pectinolytic enzymes, whereby the lag time of the system was controlled by the ratio of pectin to enzymes (Fig. 10). 

Co-immobilization Pectin, 6 g, was dissolved in 78 ml distilled water, with subsequent addition of 6 ml sodium acetate buffer (1 M, pH 4.2) and 10 g wet yeast. Silica containing immobilized enzyme (206.5 U/g dried silica or 272.2 U/g dried silica) was then mixed with the suspension at the ratio of 1.5 g of wet silica-enzyme/20 g yeast-pectin suspension. One gram of dried silica corresponded to 1.5 of wet silica. Finally, the suspension was dropped in a 0.2 M CaC solution, and 18.5 g of 4 mm spherical particles were formed after curing in a refngerator, for 18 to 20 h. 

---