Showing papers by "Arnold L. Demain published in 1982"

Saccharification of Complex Cellulosic Substrates by the Cellulase System from Clostridium thermocellum.

Abstract: True cellulase activity has been demonstrated in cell-free preparations from the thermophilic anaerobe Clostridium thermocellum Such activity depends upon the presence of Ca and a thiol-reducing agent of which dithiothreitol is the most promising Under these conditions, native (cotton) and derived forms of cellulose (Avicel and filter paper) were all extensively solubilized at rates comparable with cellulase from Trichoderma reesei Maximum activity of the Clostridium cellulase was displayed at 70 degrees C and at pH 57 and 61 on Avicel and carboxymethylcellulose, respectively In the absence of substrate at temperatures up to 70 degrees C, carboxymethylcellulase was much more unstable than the Avicel-hydrolyzing activity

High performance liquid chromatography (HPLC) of natural products V. The use of HPLC in the cell-free biosynthetic conversion of alpha-aminoadipyl-cysteinyl-valine (LLD) into isopenicillin N.

Abstract: Isopenicillin N (I) and penicillin N (II) were separated effectively by reversed phase HPLC as derivatives of chiral 2, 3, 4, 6-tetra- O-acetyl-β-D-glucopyranosyl isothiocyanate (III). This permitted identification of isopenicillin N isolated by HPLC during a biosynthetic cell-free experiment using α-L-aminoadipyl-L-cysteinyl-D-valine (IV) as precursor.

Germination initiation and outgrowth of spores of Bacillus brevis strain Nagano and its gramicidin S-negative mutant.

Abstract: Bacillus brevis strain Nagano and its gramicidin S-negative mutant, BI-7, were compared with respect to germination of their spores produced in several media. Germination initiation occurred in the presence of nutrient broth orL-alanine but not with inosine, glucose, glycerol or fructose; the process was activated by heat. Parental and mutant spores behaved similarly in these experiments. During outgrowth, parental spores remained in this phase of germination much longer than did mutant spores, but only when the parental spores had been harvested from a sporulation medium where significant gramicidin S synthesis had occurred. When parental spores were extracted or treated with an enzyme that hydrolyzes gramicidin S, rapid outgrowth occurred. Adding exogenous gramicidin S or the extract from parental spores to mutant spores lengthened the outgrowth in a dose-dependent manner. The uptake of labeledL-alanine by parental spores was delayed compared to mutant spores in the presence or absence of chloramphenicol. These data suggest a mechanism of action for gramicidin S whereby it interferes in membrane function, such as transport or energy metabolism, in outgrowing spores.

Studies on the overproduction of indole-containing metabolites by a methanol-utilizing yeast : Hansenula polymorpha.

Abstract: Production of indole-containing metabolites (“indoles”) from methanol has been studied using a mutant ofHansenula polymorpha resistant to 5-fluorotryptophan. Whereas the wild-type culture produces only a small amount of indoles, the mutant is partially deregulated and overproduces indoles. Indoles production was studied in batch and continuous culture and in a washed-cell system. When the pH was above 4.0, indoles production was growth-associated, in both minimal and complex media, and batch or continuous culture. When the pH was below or equal to 4.0, a low phosphate concentration was found to improve production. In a phosphate-deficient washed-cell suspension system, the addition of an amino acid such as methionine at 5 mM increased specific productivity by more than 60%. Addition of cycloheximide at 50 mg/L decreased residual growth and increased maximum productivity of indoles by more than 60%. When the antibiotic was added at 1000 mg/L, growth was completely inhibited and indoles production continued for about 35 h.