Search PubMed⌕ Search

Biomedical subjects

J C Linden

Publications and source records attributed to J C Linden.

9 recordsLinked to original sources
PubMed2003

Optimization of phytase production by solid substrate fermentation.

The production of phytase by three feed-grade filamentous fungi ( Aspergillus ficuum NRRL 3135, Mucor racemosus NRRL 1994 and Rhizopus oligosporus NRRL 5905) on four commonly used natural feed ingredients (canola meal, cracked corn, soybean meal, wheat bran) was studied in solid substrate fermentation (SSF). A. ficuum NRRL 3135 had the highest yield [15 IU phytase activity/g dry matter (DM)] on wheat bran. By optimizing the supplementation of wheat bran with starch and (NH(4))(2)SO(4), phytase production increased to 25 IU/g DM. Optimization was carried out by Plackett-Burman and central composite experimental designs. Using optimized medium, phytase, phosphatase, alpha-amylase and xylanase production by A. ficuum NRRL 3135 was studied in Erlenmeyer flask and tray SSF. By scaling up SSF from flasks to stationary trays, activities of 20 IU phytase activity/g DM were reproducibly obtained.

6-Phytase↗
PubMed2001

Gas concentration effects on secondary metabolite production by plant cell cultures.

One aspect of secondary metabolite production that has been studied relatively infrequently is the effect of gaseous compounds on plant cell behavior. The most influential gases are believed to be oxygen, carbon dioxide and other volatile hormones such as ethylene and methyl jasmonate. Organic compounds of interest include the promising antimalarial artemisinin (known as "qing hao su" in China where it has been a folk remedy for centuries) that is produced by Artemisia annua (sweet wormwood) and taxanes used for anticancer therapy that are produced by species of Taxus (yew). The suspension cultures of both species were grown under a variety of dissolved gas conditions in stoppered culture flasks and under conditions of continuous headspace flushing with known gas mixtures. An analysis is presented to show the culture conditions are such that equilibrium between the culture liquid and gas head-space is assured. The growth rate of the cells and their production rates of artemisinin and paclitaxel were determined. These and other parameters are correlated as functions of the gas concentrations. Interdependence of ethylene and methyl jasmonate is also explored with respect to regulation of secondary metabolite formation.

Acetates↗
PubMed2000

Simultaneous saccharification and cofermentation of peracetic acid-pretreated biomass.

Previous work in our laboratories has demonstrated the effectiveness of peracetic acid for improving enzymatic digestibility of lignocellulosic materials. The use of dilute alkali solutions as a pre-pretreatment prior to peracetic acid lignin oxidation increased carbohydrate hydrolysis yields in a synergistic as opposed to additive manner. Deacetylation of xylan is easily achieved using dilute alkali solutions under mild conditions. In this article, we evaluate the effectiveness of peracetic acid combined with an alkaline pre-pretreatment through simultaneous saccharification and cofermentation (SSCF) of pretreated hybrid poplar wood and sugar cane bagasse. Respective ethanol yields of 92.8 and 91.9% of theoretical are achieved using 6% NaOH/15% peracetic acid-pretreated substrates and recombinant Zymomonas mobilis CP4/pZB5. Reduction of acetyl groups of the lignocellulosic materials is demonstrated following alkaline pre-pretreatments. Such processing may be helpful in reducing peracetic acid requirements. The influence of deacetylation is more significant in combined pretreatments using lower peracetic acid loadings.

Biomass↗
PubMed1984

De Novo Maltotriose Biosynthesis from the Reducing End by Spinacia oleracea L. Chloroplasts.

The distribution of (14)C in the various glucose residues of maltotriose was studied as a function of time of photosynthesis of isolated chloroplasts of spinach (Spinacia oleracea L.) using (14)CO(2). The distribution of label showed that the reducing-end glucose residue was labeled first and the label subsequently distributed to the second and third glucose residues at approximately equal rates.A mechanism for the distribution of label and the synthesis of maltotriose from the reducing end is presented. The mechanism has postulated to be the same as that for the maltose synthase recently described by Schilling. Maltose biosynthesis from alpha-d-glucose-1-phosphate was characterized as involving two glucosyl intermediates by a double displacement mechanism with inversion of configuration. The mode of enzymic action by which maltosyl intermediates were transferred to glucosyl intermediates was consistent with the fractional distribution of radioactivity found in each glucose unit of maltotriose during short term photosynthesis experiments.

Journal Article↗
PubMed1974

Properties of glucosyltransferase and glucan transferase from spinach.

A glucosyl and a glucosyl-glucan transferase activity from spinach (Spinacia oleracea L. var. Matador) leaves have been partially purified and characterized. The latter activity (fraction 1 after diethylaminoethylcellulose chromatography) is responsible for the transfer of glucosyl as well as of maltosyl, maltotriosyl, and higher homologous residues to glucose giving rise to maltose and the correspondingly larger molecules. This fraction also shows beta-amylase activity. The transfer takes place only to glucose; maltose, as well as other alpha-1,4-glucans, serve as donors. The enzyme fraction 2 is amylase-free and catalyzes only the transfer of glucosyl moieties, again with high acceptor specificity to glucose. Maltose and larger alpha-1, 4-glucans, with the exception of maltotriose and maltotetraose, act as donors. The physiological function of these enzymes may be the formation of oligosaccharide primers for starch synthetase or phosphorylase.

Journal Article↗
PubMedDate not supplied

Methyl jasmonate induced production of taxol in suspension cultures of Taxus cuspidata: ethylene interaction and induction models.

Suspension cultures of Taxus cuspidata were challenged with various concentrations and combinations of methyl jasmonate and ethylene. Taxol productivity increased 19-fold when T. cuspidata suspension cultures were exposed to 5 ppm ethylene and 10 microM methyl jasmonate. This increase was 15-fold when either 0 or 10 ppm ethylene was combined with 10 microM methyl jasmonate. The induction of taxol occurred within 51 h after elicitation and would reduce fermentation times and costs. Ethylene concentration at 50 ppm had an inhibitory effect on taxol production but not on phosphate uptake rate, suggesting independent regulation of taxol and physiological functions of the cell. A simple induction model is proposed to explain the action and effects of both ethylene and methyl jasmonate with regard to receptor binding and regulatory systems in plants.

Acetates↗
PubMedDate not supplied

Kinetic studies of paclitaxel production by Taxus canadensis cultures in batch and semicontinuous with total cell recycle.

Suspension cultures of Taxus canadensis were elicited with methyl jasmonate (MJ) under defined headspace ethylene concentrations. Kinetic studies of growth, nutrient consumption, pH variation, and paclitaxel accumulation were conducted in batch cultures and semicontinuous culture with total cell recycle. A dramatic increase of paclitaxel was obtained when the cultures were elicited with 100 microM MJ, but cell growth was thereby arrested. Supplementation of acetyl-CoA and MJ to the culture proved to be another way to improve paclitaxel yields. Using semicontinuous culture with total cell recycle, paclitaxel accumulation was increased by a factor of 4.0 relative to that in the batch culture during 35 days of cultivation.

Acetates↗
PubMedDate not supplied

Production of alpha-amylase with Aspergillus oryzae on spent brewing grain by solid substrate fermentation.

Ten Aspergillus oryzae strains were screened in solid substrate fermentation for alpha-amylase production on spent brewing grain (SBG) and on corn fiber. SBG proved to be a better substrate for enzyme production than corn fiber. A Plackett-Burman experimental design was used to optimize the medium composition for the best strain. Solid substrate fermentation on optimized medium with A. oryzae NRRL 1808 (=ATCC 12892) strain in stationary 500-mL Erlenmeyer flask culture yielded 4519 U of alpha-amylase/g of dry matter substrate in 3 d. The whole solid substrate fermentation material (crude enzyme, in situ enzyme) may be considered a cheap biocatalytic material for animal feed rations and for bioalcohol production from starchy materials.

Aspergillus oryzae↗