Cassava

Lupine seed, though used primarily in animal feeds (see Feeds AND FEED ADDITIVES), does have potential for use in human appHcations as a replacement for soy flour, and is reported to contain both trypsin inhibitors and hemagglutenins (17). The former are heat labile at 90°C for 8 minutes the latter seem much more stable to normal cooking temperatures. Various tropical root crops, including yam, cassava, and taro, are also known to contain both trypsin and chymotrypsin inhibitors, and certain varieties of sweet potatoes may also be impHcated (18). 

Thiocyanate ion, SCN , inhibits formation of thyroid hormones by inhibiting the iodination of tyrosine residues in thyroglobufin by thyroid peroxidase. This ion is also responsible for the goitrogenic effect of cassava (manioc, tapioca). Cyanide, CN , is liberated by hydrolysis from the cyanogenic glucoside finamarin it contains, which in turn is biodetoxified to SCN. 

Brot masse, /. breadstuff. raffinade, /. loaf sugar. rindei /. bread crust. teigt m. bread dough, -wurzel, /. cassava yam. zucker, m. loaf sugar. 

The hydroxynitrile lyase (HNL)-catalyzed addition of HCN to aldehydes is the most important synthesis of non-racemic cyanohydrins. Since now not only (f )-PaHNL from almonds is available in unlimited amounts, but the recombinant (S)-HNLs from cassava (MeHNL) and rubber tree (HbHNL) are also available in giga units, the large-scale productions of non-racemic cyanohydrins have become possible. The synthetic potential of chiral cyanohydrins for the stereoselective preparation of biologically active compounds has been developed during the last 15 years. 

Until 1987, the (R)-PaHNL from almonds was the only HNL used as catalyst in the enantioselective preparation of cyanohydrins. Therefore, it was of great interest to get access to HNLs which catalyze the formation of (5 )-cyanohydrins. (5 )-SbHNL [EC 4.1.2.11], isolated from Sorghum bicolor, was the first HNL used for the preparation of (5 )-cyanohydrins. Since the substrate range of SbHNL is limited to aromatic and heteroaromatic aldehydes as substrates, other enzymes with (5 )-cyanoglycosides have been investigated as catalysts for the synthesis of (5 )-cyanohydrins. The (5 )-HNLs from cassava (Manihot esculenta, MeHNL) and from Hevea brasiliensis (HbHNL) proved to be highly promising candidates for the preparation of (5 )-cyanohydrins. Both MeHNL and HbHNL have been overexpressed successfully in Escherichia coli, Saccharomyces cerevisiae and Pichia pastoris. 

Pectinases from Rhizopus sp. Efficient in Enhancing the Hydrolyzation of Raw Cassava Starch Purification and Characterization... 

Digestion of raw starch from ground cassava tuber... 

Pectinase from Rhizopus sp. 26R showed high efficiency in enhancing the digestion of raw starch from whole cassava tuber when it was mixed with the glucoamylase. At the 1 hour of the reaction, the mixed enzymes gave the most efficient digestibility with hydrolyzation rate twice faster, than that when glucoamylase was used alone and about 3 times faster than when pectinases... 

According to the ability of the pectinase of Rhizopus sp. 26R that could efficiently enhance the hydrolyzation of raw starch from whole cassava tuber. 

Cassava is one of an important economic plants of Thailand. Thailand exported cassava products eg. cassava chip, peUet, flour and starch, etc. which are low value. The amount of the products was approx. 20 milhon metrictons a year in 1993. However, by the process, some carbohydrates in cassava tuber still waste and further cause pollution. 

Microorganism Rhizopus sp. 26R, a fungal strain isolated in Thailand which capable of hydrolyzation of raw cassava starch (Figure 1). 

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. 

Figure 3 Pectinase activity in 20 g of solid substrates composting of wheat bran, rice bran and rice husk (18 0 2) with the addition of 1 g raw starch from cassava tuber, 1 g pectin or 0.5 g yeast extract.

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). 

The efficiency in raw cassava starch hydrolyzation of pectinases from Rhizopus sp. 26R compared with a commercial pectinase when mixed with Glucoamylase from Aspergillus niger J8. 

When compare the efficiency in enhancing the hydrolyzation of raw cassava starch between pectinases from Rhizopus sp. 26R and the commercial pectinase at periods of time (Figure 10). 

While using of commercial pectinase with glucoamylase showed less efficient in enhancing the hydrolyzation of starch. In the 2nd, 4th, 6th and 8th hours, the commercial one could enhance the hydrolyzation only 1.2, 1.4, 1 and 1 time, respectively. Therefore, pectinases of Rhizopus sp. 26R was more efficient in enhancing the digestion of raw cassava starch more than the commercial one when used with glucoamylase. 

The production of the pectinases in the sohd substrates composed of wheat bran, rice bran and rice husk (6 12 2) was considerably very low. The spore inoculum of Rhizopus sp. 26R was prepared on raw cassava starch agar which the cost estimation was US 1.0 per 1 litre. Wheat bran, rice bran and rice husk were approx. US 64 per 50 kg. The total cost of the production of pectinases from Rhizopus sp. 26R in the sohd substrates, when considered only on the substrates was estimated to be only US 178 - 180 for 10 million units of crude pectinase. 

The enzyme production in the solid substrates composed of wheat bran and rice husk (18 2) could be increased by the addition of either 1 g raw cassava starch or 1 g pectin to a 20 g substrates. The enzyme activity increased approx. 1.7 and 2.4 times, respectively. 

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). 

The pectinases produced in solid substrates from Rhizopus sp. 26R showed the efficiency in enhancing the activity of the glucoamylase in digestion of raw-ground-cassava tuber higher than that of the commercial one. 

The mechanism for sedimentation (clarification) is based on the density difference between SS and liquid. In addition, SS with larger particle sizes can settle down more easily. Rectangular tanks, circular tanks, combination flocculator-clarifiers, and stacked multilevel clarifiers can be used.14 Oliveira et al.15 reported that flocculation and sedimentation were conducted in the cassava meal industry and reduced the effluent concentration of organics from 14,000 to 2000 mg/L in the bench-scale reactor, with a hydraulic retention time (HRT) of 37 min. 

Oliveira, M.A., Reis, E.M., and Nozaki, J., Biological treatment of wastewater from the cassava meal industry, Environmental Research, 85, 177-183, 2001. 

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