Biomedical subjects

Michael H Penner

Publications and source records attributed to Michael H Penner.

3 recordsLinked to original sources

PubMed2005

Enzymatic saccharification and fermentation of xylose-optimized dilute acid-treated lignocellulosics.

The cellulose reactivity of two lignocellulosic feedstocks, switchgrass and poplar, was evaluated under straight saccharification (SS) and simultaneous saccharification and fermentation (SSF) conditions following dilute sulfuric acid pretreatments designed for optimum xylose yields. The optimum pretreatment conditions, within the constraints of the experimental system (Parr batch reactor), were 1.2% acid, 180 degrees C, and 0.5 min for switchgrass and 1% acid, 180 degrees C, and 0.56 min for poplar. The cellulase enzyme preparation was from Trichoderma reesei and fermentations were done with Saccharomyces cerevisiae. Time courses for SS were monitored as the sum of glucose and cellobiose; those for SSF as the sum of glucose, cellobiose, and ethanol. Percentage conversions under SS conditions were 79.1% and 91.4% for the pretreated poplar and switchgrass feedstocks, respectively. Analogous values under SSF conditions were 73.0% and 90.3% for pretreated poplar and switchgrass, respectively.

Cell Culture Techniques↗

PubMed2004

Cellulose-based chromatography for cellooligosaccharide production.

The potential of using cellulose stationary phases for the chromatographic fractionation of cellooligosaccharide preparations has been explored. The impetus for the work is the current interest in using cellooligosaccharides as functional nondigestible oligosaccharides in foods. The conceptual studies illustrate the potential of using ethanol-water mobile phases in conjunction with cellulose stationary phases for cellooligosaccharide fractionation. Cellooligosaccharide solubility in ethanol-water mixtures and their elution order from cellulose-based columns using ethanol-water mobile phases were shown to be in line with their degree of polymerization (DP), with the higher DP cellooligosaccharides being less soluble and having longer retention times. The retention volume for all COS increased with increased temperature. Both microcrystalline and fibrous cellulose preparations were shown to work as chromatographic stationary phases. The application experiments demonstrate the potential of using cellulose stationary phases for the cleanup and fractionation of cellooligosaccharide mixtures generated via acid-catalyzed hydrolysis of cellulose.

Cellulose↗

PubMed2004

Quantitative analysis of cellulose-reducing ends.

Methods for the quantification of total and accessible reducing ends on traditional cellulose substrates have been evaluated because of their relevance to enzyme-catalyzed cellulose saccharificaion. For example, quantification of accessible reducing ends is likely to be the most direct measure of substrate concentration for the exo-acting, reducing end-preferring cellobiohydrolases. Two colorimetric assays (dinitrosalicylic acid [DNS] and bicinchoninic acid [BCA] assay ) and a radioisotope approach (NaB3H4 labeling) were evaluated for this application. Cellulose substrates included microcrystalline celluloses, bacterial celluloses, and filter paper. Estimates of the number of reducing ends per unit mass cellulose were found to be dependent on the assay system (i.e. the DNS and BCA assays gave strikingly different results). DNS-based values were several-fold higher than those obtained using the BCA assay, with fold-differences being substrate specific. Sodium borohydride reduction of celluloses, using cold or radiolabeled reagent under relatively mild conditions, was used to assess the number of surface (solvent-accessible) reducing ends. The results indicate that 30-40% of the reducing ends on traditional cellulose substrates are not solvent accessible; that is, they are buried in the interior of cellulose structures and thus not available to exo-acting enzymes.

Biotechnology↗