A synergistic effect of some amylolytic enzymes on the saccharification of raw corn starch by the raw starch digesting amylase of Aspergillus sp . K-27 was investigated from an industrial point of view. The degree of digestion of raw corn starch increased concomitantly with an increasing the dosage of K-27 amylase, but the yield of glucose formed from starch decreased conversely under the conditions used. Bacterial α-amylases accelerated the digestion rate of raw starch by K-27 amylase; the yield of glucose, however, decreased when the reaction was performed at higher enzyme dosages. Pullulanase and oligo-1, 6-glucosidase increased effectively the yield of glucose . The most effective combination of these enzymes with K-27 amylase on the saccharification of raw corn starch was as follows: 114 U/g of a-amylase+8.2 U/g of pullulanase+100 U/g of K-27 amylase (the digestion rate, 79.5%; the yield of glycose, 94.5%); or 1.5 U/g of oligo-1, 6-glucosidase added to the mixture of these enzymes(the digestion rate, 81.3%; the yield of glucose, 94.4%). No difficulty was observed in the separation of soluble saccharides and raw cornstarch from the mother liquor by filtration under the conditions tested .

View full abstract

For the purpose of a continuous production of maltotetraose, we tried to immobilize the exo-maltotetraohydrolase [EC. 3 .2.1.60]. Among two hundred kinds of commercial resins examined, a macroporous hydrophobic resin "Diaion HP50" was the best carrier for the immobilization of exo-maltotetraohydrolase . The optimum pH curve of the immobilized enzyme slightly shifted to the acidic side. The pH stability was improved by immobilization. The enzyme was stable retaining more than 90 of its original activity in the range of pH 5.5-9.5. The optimum reaction temperature of the enzyme increased about 10°C. Thermostability was also improved by immobilization, and increased about 5-7°C compared to the native enzyme . Not many differences were observed between the immobilized and native enzymes on the effects of various metal ions and SH-inhibitors . When reduced-soluble starch was used as the substrate, the Km value of the immobilized enzyme was sixty times as large as that of nativeenzyme. A continuous production of maltotetraose was also investigated by using the immobilized exo-maltotetraohydrolase column reactor and some reaction conditions for the production of maltotetraose were established.

View full abstract

Living organisms produce a wide variety of polymeric carbohydrates, of which cellulose is the most abundant. The main deterioration of cellulose is caused by microorganisms, and the biological degradation of cellulosic substances is an extremely important process for the maintenance of the carbon balance in nature. Since crystalline cellulose is an insoluble substance with a supramolecular structure, the enzymological approaches to this substrate are rather complicated and difficult . In most cellulolytic microorganisms, several cellulase components together constitute a "cellulase system" and cellulosic materials are converted to soluble sugars by their synergistic action . To understand completely the biodegradation mechanism of cellulose, therefore, the strict purification and characterization of each cellulase component is absolutely necessary . This review describes the cellulolytic enzymes and focuses on the mechanism of their action . It is divided into seven sections and includes the historical background of cellulase . Our recent findings concerning the enzyme mechanisms involved in native cellulose degradation are also described.

View full abstract