Feedback regulation and the intracellular protein profile of Streptomyces griseus in a cycloheximide fermentation

Two-dimensional gel electrophoresis (2-D PAGE) was used to study the intracellular protein profile of Streptomyces griseus in relation to cycloheximide (CH) biosynthesis. Four proteins (CR1-CR4) were found to be significantly and specifically repressed by addition of the antibiotic (1 g/l at 72 h) to a producing fermentation. Synthesis of these proteins was specific to the idiophase, concurrent with CH production. Initial addition of CH to the production medium resulted in slightly lower synthesis rates of two of the proteins (CR1 and CR2), while significantly delaying the onset of synthesis of the other two (CR3 and C4). Finally, neutral polymetric resin was added to the fermentation to alleviate feedback regulation of CH synthesis, giving roughly a twofold increase in the antibiotic production rate. Production of proteins CR3 and CR4 was increased approximately tenfold immediately following resin addition, but returned to the control rate of synthesis after 24 h.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46761/1/253_2004_Article_BF00166779.pd

Phosphate feeding to permit growth while maintaining secondary product synthesis

Maintaining high metabolic activities for extended periods by feeding small amounts of the growth limiting nutrient was examined for the production of cycloheximide by Streptomyces griseus . Batch studies indicated that increased initial phosphate levels led to increased cell concentrations, stimulated glucose utilization, and over a limited range (<0.6 g/l KH 2 PO 4 ) did not adversely affect cycloheximide production rates. Semi-continuous phosphate feeding was observed to permit limited cell growth, and to enhance metabolic activities (i. e. glucose utilization). The effect of semi-continuous phosphate feeding on antibiotic production depended on the feed rate, with high feed rates suppressing production.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46756/1/253_2004_Article_BF00451634.pd

The effect of feedback regulation and in situ product removal on the conversion of sugar to cycloheximide by Streptomyces griseus

An addition of cycloheximide to cycloheximide-producing Streptomyces griseus cultures resulted in reductions in the production rate and in the conversion of sugar into cycloheximide. In situ cycloheximide adsorption was observed to enhance: total cycloheximide titers; productivities; and the conversion of sugar to cycloheximide. During the secondary metabolite-producing phase, sugar consumption was observed to be linearly dependent on cycloheximide productivity. From this analysis a true product yield and maintenance coefficient were estimated to be 0.08 g cycloheximide/g glucose and 0.028 g glucose/g cell-h, respectively. The sixfold difference between this true product yield and a theoretical value obtained from knowledge of the biosynthetic pathway is discussed. Since the maintenance sugar requirement for cycloheximide production is large, stimulation of biosynthesis through in situ adsorption significantly increases the overall efficiency of sugar conversion to this secondary metabolite.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46130/1/203_2004_Article_BF00406560.pd