Quantitative estimate of the effect of cellulase components during degradation of cotton fibers

Research on Chemically Deuterated Cellulose Macroperformance and Fast Identification

Chemically deuterated cellulose fiber was expected to provide novel applications due to its spectral, biological, and kinetic isotope effect. In this research, the performance of the chemically deuterated cotton fibers, including their mechanical property, enzymatic degradation performance, effect on bacterial treatment, and fast identification (near-infrared modeling) was investigated. The breaking tenacity of the deuterated cotton fibers was slightly lower, which might be attributed to the structural damage during the chemical deuteration. The glucose yield by enzymatic hydrolysis was less than that of the protonic cotton fibers, implying the deuterated fibers are less sensitive to enzymatic degradation. Furthermore, the deuterated fibers could promote the growth of bacteria such as Escherichia. coli, which was associated with the released low-level deuterium content. At last, the near-infrared technique combined with partial least squares regression successfully achieved a fast identification of the protiated and deuterated cotton fibers, which significantly promoted the potential application of deuterated cellulose as anticounterfeiting materials (e.g., special paper).

Determination of the action modes of cellulases from hydrolytic profiles over a time course using fluorescence-assisted carbohydrate electrophoresis

Fluorescence-assisted carbohydrate electrophoresis (FACE) is a sensitive and simple method for the separation of oligosaccharides. It relies on labeling the reducing ends of oligosaccharides with a fluorophore, followed by PAGE. Concentration changes of oligosaccharides following hydrolysis of a carbohydrate polymer could be quantitatively measured continuously over time using the FACE method. Based on the quantitative analysis, we suggested that FACE was a relatively high-throughput, repeatable, and suitable method for the analysis of the action modes of cellulases. On account of the time courses of their hydrolytic profiles, the apparent processivity was used to show the different action modes of cellulases. Cellulases could be easily differentiated as exoglucanases, β-glucosidases, or endoglucanases. Moreover, endoglucanases from the same glycoside hydrolases family had a variety of apparent processivity, indicating the different modes of action. Endoglucanases with the same binding capacities and hydrolytic activities had similar oligosaccharide profiles, which aided in their classification. The hydrolytic profile of Trichoderma reesei Cel12A, an endoglucanases from T. reesei, contained glucose, cellobiose, and cellotriose, which revealed that it may have a new glucosidase activity, corresponding to that of EC 3.2.1.74. A hydrolysate study of a T. reesei Cel12A-N20A mutant demonstrated that the FACE method was sufficiently sensitive to detect the influence of a single-site mutation on enzymatic activity.

Purification and characterisation of endo-β-1,4-glucanase and laminarinase enzymes from the gecarcinid land crab Gecarcoidea natalis and the aquatic crayfish Cherax destructor

Laminarinase and endo-β-1,4-glucanase were purified and characterised from the midgut gland of the herbivorous land crab Gecarcoidea natalis and the crayfish Cherax destructor. The laminarinase isolated from G. natalis was estimated to have a molecular mass of 41 kDa by SDS-PAGE and 71 kDa by gel filtration chromatography. A similar discrepancy was noted for C. destructor. Possible reasons for this are discussed. Laminarinase (EC 3.2.1.6) from G. natalis had a Vmax of 42.0 μmol reducing sugars produced min–1 mg protein–1, a Kmof 0.126% (w/v) and an optimum pH range of 5.5–7, and hydrolysed mainlyβ-1,3-glycosidic bonds. In addition to the hydrolysis ofβ-1,3-glycosidic bonds, laminarinase (EC 3.2.1.39) from C. destructor was capable of significant hydrolysis of β-1,4-glycosidic bonds. It had a Vmax of 19.6 μmol reducing sugars produced min–1 mg protein–1, a Km of 0.059% (w/v) and an optimum pH of 5.5. Laminarinase from both species produced glucose and other short oligomers from the hydrolysis of laminarin. Endo-β-1,4-glucanase (EC 3.2.1.4) from G. natalis had a molecular mass of 52 kDa and an optimum pH of 4–7. It mainly hydrolysed β-1,4-glycosidic bonds, but was also capable of significant hydrolysis of β-1,3-glycosidic bonds. Two endo-β-1,4-glucanases, termed 1 and 2, with respective molecular masses of 53±3 and 52 kDa, were purified from C. destructor. Endo-β-1,4-glucanase 1 was only capable of hydrolysingβ-1,4-glycosidic bonds and had an optimum pH of 5.5. Endo-β-1,4-glucanases from both species produced some glucose, cellobiose and other short oligomers from the hydrolysis of carboxymethyl cellulose.

A review of feeding and nutrition of herbivorous land crabs: adaptations to low quality plant diets

This paper reviews the nutritional ecology, the digestive physiology, and biochemistry of herbivorous land crabs and the adaptations that they possess towards a diet of plant material. Land crab species that breathe air and forage out of water can be divided into three feeding specialisations: primarily carnivorous, deposit feeders feeding on micro-organisms and organic matter in the sediment, and herbivores consuming mainly plant material and its detritus. The last forms the focus of this review. The diets of the herbivores are low in nitrogen and high in carbon, are difficult to digest since they contain cellulose and hemicellulose, and may disrupt digestion due to the presence of tannins. Herbivorous crustaceans are able to efficiently utilise plant material as their primary nutrient source and are indeed able to meet their nitrogen requirements from it. Herbivorous land crabs display a range of adaptations towards a low nitrogen intake and these are discussed in this review. They also appear to endogenously produce cellulase and hemicellulase enzymes for the digestion of cellulose and hemicellulose. Generalised and specific adaptations allow them to inhibit the potentially negative digestive effects of tannins. To digest plant material, they possess a plastic digestive strategy of high food intake, short retention time, high assimilation of cell contents, and substantial digestion of cellulose and hemicellulose.

A novel approach for estimating growth phases and parameters of bacterial population in batch culture

Using mathematical analysis, a new method has been developed for studying the growth kinetics of bacterial populations in batch culture. First, sampling data were smoothed with the spline interpolation method. Second, the instantaneous rates were derived by numerical differential techniques and finally, the derived data were fitted with the Gaussian function to obtain growth parameters. We named this the Spline-Numerical-Gaussian or SNG method. This method yielded more accurate estimates of the growth rates of bacterial populations and new parameters. It was possible to divide the growth curve into four different but continuous phases based on changes in the instantaneous rates. The four phases are the accelerating growth phase, the constant growth phase, the decelerating growth phase and the declining phase. Total DNA content was measured by flow cytometry and varied depending on the growth phase. The SNG system provides a very powerful tool for describing the kinetics of bacterial population growth. The SNG method avoids the unrealistic assumptions generally used in the traditional growth equations.

Changes in the structural properties and rate of hydrolysis of cotton fibers during extended enzymatic hydrolysis

An extended enzymatic hydrolysis of cotton fibers by crude cellulase from Trichoderma pseudokoningii S-38 is described with characterization of both the enzyme changes of activities and cellulose structure. The hydrolysis rates declined drastically during the early stage and then slowly and steadily throughout the whole hydrolysis process the same trend could be seen during the following re-hydrolysis process. Morphological and structural changes to the fibers, such as swelling, frequent surface erosion, and variation in the packing and orientation of microfibrils, were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Observation of X-ray diffraction and IR spectra suggests that the hydrolysis process results in a gradual increase in the relative intensity of the hydrogen bond network, and a gradual decrease in the apparent crystal size of cellulose. The I(alpha) crystal phase was hydrolyzed more easily than was the I(beta) crystal phase. Apart from the inactivation of CBHs activity, changes in the packing and arrangement of microfibrils and the structural heterogeneity of cellulose during hydrolysis could be responsible for the reduction in the rate of reaction, especially in its later stages. The results indicate that the enzymatic hydrolysis of cellulose occurs on the outer layer of the fiber surface and that, following this, the process continues in a sub-layer manner.