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Author

G. L. Miller

Bio: G. L. Miller is an academic researcher. The author has contributed to research in topic(s): Reducing sugar & 3,5-Dinitrosalicylic acid. The author has an hindex of 1, co-authored 1 publication(s) receiving 23198 citation(s).

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23,198 citations


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C. Stan Tsai1
14 Apr 2006

3,211 citations

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TL;DR: In this paper, a collaborative investigation of assays for endo-1,4-β-xylanase activity based on production of reducing sugars from polymeric 4-O-methyl glucuronoxylan was conducted.
Abstract: Twenty laboratories participated in a collaborative investigation of assays for endo-1,4-β-xylanase activity based on production of reducing sugars from polymeric 4-O-methyl glucuronoxylan. The substrates and methods already in use in the different laboratories were first recorded and the apparent activities obtained using these methods in the analysis of a distributed enzyme sample were compared. The standard deviation of the results reported in this analysis was 108% of the mean. Significant reduction in interlaboratory variation was obtained when all the participants used the same substrate for activity determination, each with their own assay procedure. The level of agreement was further improved when both the substrate and the method procedure were standardized. In a round robin testing of a single substrate and method, including precise instructions for enzyme dilution, the standard deviation between the results after the rejection of two outliers was 17% of the mean. This figure probably reflects the inherently poor reproducibility of results when using only partially soluble, poorly defined and rather impure polymeric substrates. The final level of variation was however low enough to allow meaningful comparison of results obtained in different laboratories when using the standardized assay substrate and method procedure. Fifteen laboratories also participated in preliminary testing of an assay based on the release of dyed fragments from 4-O-methyl glucuronoxylan dyed with Remazol Brilliant Blue dye. High values of the coefficients of correlation indicated good linearity between the amount of dyed fragments released and enzyme concentration. The relative standard deviations of the results obtained by fifteen laboratories were about 30% for an optimum range of xylanase activity in the reaction mixture.

2,209 citations

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TL;DR: In this paper, the authors review quantitative cellulase activity assays using soluble and insoluble substrates, and focus on their advantages and limitations, and hypothesize that continuous culture using insoluble cellulosic substrates could be a powerful selection tool for enriching beneficial cellulase mutants from the large library displayed on the cell surface.
Abstract: Cellulose is the most abundant renewable natural biological resource, and the production of biobased products and bioenergy from less costly renewable lignocellulosic materials is important for the sustainable development of human beings. A reduction in cellulase production cost, an improvement in cellulase performance, and an increase in sugar yields are all vital to reduce the processing costs of biorefineries. Improvements in specific cellulase activities for non-complexed cellulase mixtures can be implemented through cellulase engineering based on rational design or directed evolution for each cellulase component enzyme, as well as on the reconstitution of cellulase components. Here, we review quantitative cellulase activity assays using soluble and insoluble substrates, and focus on their advantages and limitations. Because there are no clear relationships between cellulase activities on soluble substrates and those on insoluble substrates, soluble substrates should not be used to screen or select improved cellulases for processing relevant solid substrates, such as plant cell walls. Cellulase improvement strategies based on directed evolution using screening on soluble substrates have been only moderately successful, and have primarily targeted improvement in thermal tolerance. Heterogeneity of insoluble cellulose, unclear dynamic interactions between insoluble substrate and cellulase components, and the complex competitive and/or synergic relationship among cellulase components limit rational design and/or strategies, depending on activity screening approaches. Herein, we hypothesize that continuous culture using insoluble cellulosic substrates could be a powerful selection tool for enriching beneficial cellulase mutants from the large library displayed on the cell surface.

1,442 citations

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TL;DR: The combined results suggested that SNPs may damage the structure of bacterial cell membrane and depress the activity of some membranous enzymes, which cause E. coli bacteria to die eventually.
Abstract: The antibacterial activity and acting mechanism of silver nanoparticles (SNPs) on Escherichia coli ATCC 8739 were investigated in this study by analyzing the growth, permeability, and morphology of the bacterial cells following treatment with SNPs. The experimental results indicated 10 microg/ml SNPs could completely inhibit the growth of 10(7) cfu/ml E. coli cells in liquid Mueller-Hinton medium. Meanwhile, SNPs resulted in the leakage of reducing sugars and proteins and induced the respiratory chain dehydrogenases into inactive state, suggesting that SNPs were able to destroy the permeability of the bacterial membranes. When the cells of E. coli were exposed to 50 microg/ml SNPs, many pits and gaps were observed in bacterial cells by transmission electron microscopy and scanning electron microscopy, and the cell membrane was fragmentary, indicating the bacterial cells were damaged severely. After being exposed to 10 microg/ml SNPs, the membrane vesicles were dissolved and dispersed, and their membrane components became disorganized and scattered from their original ordered and close arrangement based on TEM observation. In conclusion, the combined results suggested that SNPs may damage the structure of bacterial cell membrane and depress the activity of some membranous enzymes, which cause E. coli bacteria to die eventually.

1,139 citations

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TL;DR: This review focuses on the microbial amylases and their application with a biotechnological perspective and α-Amylase holds the maximum market share of enzyme sales with its major application in the starch industry as well as its well-known usage in bakery.
Abstract: Amylases are one of the most important and oldest industrial enzymes. These comprise hydrolases, which hydrolyse starch molecules to fine diverse products as dextrins, and progressively smaller polymers composed of glucose units. Large arrays of amylases are involved in the complete breakdown of starch. However, α-amylases which are the most in demand hydrolyse α-1,4 glycosidic bond in the interior of the molecule. α-Amylase holds the maximum market share of enzyme sales with its major application in the starch industry as well as its well-known usage in bakery. With the advent of new frontiers in biotechnology, the spectrum of α-amylase application has also expanded to medicinal and analytical chemistry as well as in automatic dishwashing detergents, textile desizing and the pulp and paper industry. Amylases are of ubiquitous occurrence, produced by plants, animals and microorganisms. However, microbial sources are the most preferred one for large scale production. Today a large number of microbial α-amylases are marketed with applications in different industrial sectors. This review focuses on the microbial amylases and their application with a biotechnological perspective.

1,116 citations