G W Luli

Bio: G W Luli is an academic researcher from Ohio State University. The author has contributed to research in topics: Fermentation & Acetic acid. The author has an hindex of 5, co-authored 6 publications receiving 776 citations.

Comparison of growth, acetate production, and acetate inhibition of Escherichia coli strains in batch and fed-batch fermentations.

Abstract: The growth characteristics and acetate production of several Escherichia coli strains were compared by using shake flasks, batch fermentations, and glucose-feedback-controlled fed-batch fermentations to assess the potential of each strain to grow at high cell densities. Of the E. coli strains tested, including JM105, B, W3110, W3100, HB101, DH1, CSH50, MC1060, JRG1046, and JRG1061, strains JM105 and B were found to have the greatest relative biomass accumulation, strain MC1060 accumulated the highest concentrations of acetic acid, and strain B had the highest growth rates under the conditions tested. In glucose-feedback-controlled fed-batch fermentations, strains B and JM105 produced only 2 g of acetate.liter-1 while accumulating up to 30 g of biomass.liter-1. Under identical conditions, strains HB101 and MC1060 accumulated less than 10 g of biomass.liter-1 and strain MC1060 produced 8 g of acetate.liter-1. The addition of various concentrations of sodium acetate to the growth medium resulted in a logarithmic decrease, with respect to acetate concentration, in the growth rates of E. coli JM105, JM105(pOS4201), and JRG1061. These data indicated that the growth of the E. coli strains was likely to be inhibited by the acetate they produced when grown on media containing glucose. A model for the inhibition of growth of E. coli by acetate was derived from these experiments to explain the inhibition of acetate on E. coli strains at neutral pH.

A predictive and feedback control algorithm maintains a constant glucose concentration in fed-batch fermentations.

Abstract: A combined predictive and feedback control algorithm based on measurements of the concentration of glucose on-line has been developed to control fed-batch fermentations of Escherichia coli. The predictive control algorithm was based on the on-line calculation of glucose demand by the culture and plotting a linear regression to the next datum point to obtain a predicted glucose demand. This provided a predictive "coarse" control for the glucose-based nutrient feed. A direct feedback control using a proportional controller, based on glucose measurements every 2 min, fine-tuned the feed rate. These combined control schemes were used to maintain glucose concentrations in fed-batch fermentations as tight as 0.49 +/- 0.04 g/liter during growth of E. coli to high cell densities.

Glucose-stat, a glucose-controlled continuous culture.

Abstract: A predictive and feedback proportional control algorithm, developed for fed-batch fermentations and described in a companion paper (G. L. Kleman, J. J. Chalmers, G. W. Luli, and W. R. Strohl, Appl. Environ. Microbiol. 57:910-917, 1991), was used in this work to control a continuous culture on the basis of the soluble-glucose concentration (called the glucose-stat). This glucose-controlled continuous-culture system was found to reach and maintain steady state for 11 to 24 residence times when four different background glucose concentrations (0.27, 0.50, 0.7, and 1.5 g/liter) were used. The predictive-plus-feedback control system yielded very tight control of the continuous nutristat cultures; glucose concentrations were maintained at the set points with less than 0.003 standard error. Acetate production by Escherichia coli B in glucose-stats was found not to be correlated with the level of steady-state soluble-glucose concentration.

An automatic, on-line glucose analyzer for feed-back control of fed-batch growth of Escherichia coli

Abstract: A computer-assisted on-line glucose analyzer was developed for feed-back control of cell growth. Using this system the glucose consumption rate for Escherichia coli was determined to be linear during batch culture at 0.37 g/hr. On-line feed-back control of glucose concentration at 1.5±0.5 g/L was used with fed-batch cultures to produce 31.2 g dry weight of E. coli cells/L in 12 h.

Application of a microcomputer-based system to control and monitor bacterial growth.

Abstract: A modular microcomputer-based system was developed to control and monitor various modes of bacterial growth. The control system was composed of an Apple II Plus microcomputer with 64-kilobyte random-access memory; a Cyborg ISAAC model 91A multichannel analog-to-digital and digital-to-analog converter; paired MRR-1 pH, pO2, and foam control units; and in-house-designed relay, servo control, and turbidimetry systems. To demonstrate the flexibility of the system, we grew bacteria under various computer-controlled and monitored modes of growth, including batch, turbidostat, and chemostat systems. The Apple-ISAAC system was programmed in Labsoft BASIC (extended Applesoft) with an average control program using ca. 6 to 8 kilobytes of memory and up to 30 kilobytes for datum arrays. This modular microcomputer-based control system was easily coupled to laboratory scale fermentors for a variety of fermentations.

The acetate switch.

Abstract: To succeed, many cells must alternate between life-styles that permit rapid growth in the presence of abundant nutrients and ones that enhance survival in the absence of those nutrients. One such change in life-style, the “acetate switch,” occurs as cells deplete their environment of acetate-producing carbon sources and begin to rely on their ability to scavenge for acetate. This review explains why, when, and how cells excrete or dissimilate acetate. The central components of the “switch” (phosphotransacetylase [PTA], acetate kinase [ACK], and AMP-forming acetyl coenzyme A synthetase [AMP-ACS]) and the behavior of cells that lack these components are introduced. Acetyl phosphate (acetyl∼P), the high-energy intermediate of acetate dissimilation, is discussed, and conditions that influence its intracellular concentration are described. Evidence is provided that acetyl∼P influences cellular processes from organelle biogenesis to cell cycle regulation and from biofilm development to pathogenesis. The merits of each mechanism proposed to explain the interaction of acetyl∼P with two-component signal transduction pathways are addressed. A short list of enzymes that generate acetyl∼P by PTA-ACKA-independent mechanisms is introduced and discussed briefly. Attention is then directed to the mechanisms used by cells to “flip the switch,” the induction and activation of the acetate-scavenging AMP-ACS. First, evidence is presented that nucleoid proteins orchestrate a progression of distinct nucleoprotein complexes to ensure proper transcription of its gene. Next, the way in which cells regulate AMP-ACS activity through reversible acetylation is described. Finally, the “acetate switch” as it exists in selected eubacteria, archaea, and eukaryotes, including humans, is described.

Comparison of growth, acetate production, and acetate inhibition of Escherichia coli strains in batch and fed-batch fermentations.

Abstract: The growth characteristics and acetate production of several Escherichia coli strains were compared by using shake flasks, batch fermentations, and glucose-feedback-controlled fed-batch fermentations to assess the potential of each strain to grow at high cell densities. Of the E. coli strains tested, including JM105, B, W3110, W3100, HB101, DH1, CSH50, MC1060, JRG1046, and JRG1061, strains JM105 and B were found to have the greatest relative biomass accumulation, strain MC1060 accumulated the highest concentrations of acetic acid, and strain B had the highest growth rates under the conditions tested. In glucose-feedback-controlled fed-batch fermentations, strains B and JM105 produced only 2 g of acetate.liter-1 while accumulating up to 30 g of biomass.liter-1. Under identical conditions, strains HB101 and MC1060 accumulated less than 10 g of biomass.liter-1 and strain MC1060 produced 8 g of acetate.liter-1. The addition of various concentrations of sodium acetate to the growth medium resulted in a logarithmic decrease, with respect to acetate concentration, in the growth rates of E. coli JM105, JM105(pOS4201), and JRG1061. These data indicated that the growth of the E. coli strains was likely to be inhibited by the acetate they produced when grown on media containing glucose. A model for the inhibition of growth of E. coli by acetate was derived from these experiments to explain the inhibition of acetate on E. coli strains at neutral pH.