Masahiro Shiroishi

Synergistic actions of exo-type cellulases in the hydrolysis of cellulose with different crystallinities

The synergistic actions of pairs of seven different exo- and endo-type cellulases produced by Irpex lacteus (Ex-1 and En-1), Trichoderma reesei (CBH I, CBH II, and Endo-2), and Aspergillus niger (Exo-A and EG-1) were investigated using pure cellulosic materials with different crystallinities as substrates. A marked synergism was observed with certain combinations of exo-type cellulases, namely, CBH II and the other exo-type cellulases (Ex-1, CBH I, or Exo-A), when saccharification activity against crystalline and amorphous celluloses was investigated. Differences between the modes of action of each exo-type cellulase alone and in combination are not clearly observed; the production of cellobiose was accelerated during the hydrolysis of crystalline and amorphous celluloses by the combinations of exo-type cellulases, and no effective synergistic actions of the combinations of exo-type cellulases were noted in the depolymerization of crystalline cellulose. However, the synergistic actions of exo-type cellulases with CBH II caused specific changes in the surface features of highly crystalline celluloses. Characteristic morphological changes in cotton fibers (erosion and cracking of fiber surfaces) were induced at increasing rates by the combination of CBH II and Ex-1 or Exo-A. In contrast, destruction and subdivision of fibrils, which resulted in the pronounced fibrillation of cotton fibers, were observed after the treatment of cotton fibers with CBH II and CBH I. It was suggested that CBH II may be one of the key enzymes involved in the synergistic actions during cellulose hydrolysis.

Improvement in the productivity of xylooligosaccharides from waste medium after mushroom cultivation by hydrothermal treatment with suitable pretreatment

The effective xylooligosaccharides (XOs) production from the waste medium after mushroom cultivation (WM) was investigated. The WM contains rich nutrients (protein, etc.) which induce Maillard reaction with reducing sugars under hydrothermal conditions. To improve the productivity of XOs, the suitable pretreatment combined with washing and grinding was investigated, and subsequently hydrothermal treatment was demonstrated with batch type and continuous flow type reactor. The washing pretreatment with hot water of 60 degrees C was effective to remove nutrients from the WM, and it led to prevent brownish discoloration on the hydrothermal treatment. On the basis of experimental data, industrial XOs production processes consisting of the pretreatment, hydrothermal treatment and purification step was designed. During the designed process, 2.3 kg-dry of the purified XOs was produced from 30 kg-wet of the WM (15% yield as dry basis weight). Theoretical yield of XOs attained to 48% as xylan weight in the WM.

Some characteristics of three groups in Flammulina velutipes classified by analysis of esterase isozymes

Abstract Analysis of isozymes was carried out against wild and cultivated commercial stocks of Flammulina velutipes to analyze their genetic differences. Esterase isozymes from F. velutipes showed many bands and variations among the different stocks on the gel. The stocks of F. velutipes in Japan were largely classified into three groups (tentatively named groups A, B, and C) according to the cluster analysis of esterase isozymes. Some characteristics of the three groups were examined. Group C was characterized by a larger spore size, slower spawn running, and a paler pileus color than groups A and B. Furthermore, group B showed a smaller spore size, slower spawn running, and paler pileus color than group A.