The inhibitory effect of butanol on yeast growth has been studied for the strain Candida utilis ATCC 8205 growing aerobically on butanol under batch conditions. A mathematical expression was then proposed to fit the kinetic pattern of butanol inhibition on the specific growth rate: micro = micro mS/Ks + S [1 - S/Sm]n. The maximum allowable butanol concentration above which cells do not grow was predicted to be 9.16g/L. The proposed model appears to accurately represent the experimental data obtained in this study and the literature data developed for a variety of batch culture systems at widely ranging substrate concentrations.

Generalization of monod kinetics for analysis of growth data with substrate inhibition.

This study examined the hypothesis that solid surfaces may stimulate attached bacteria to produce exopolymers. Addition of sand to shake-flask cultures seemed to induce exopolymer synthesis by a number of subsurface isolates, as revealed by optical microscopy. Several additional lines of evidence indicated that exopolymer production by attached cells (in continuous-flow sand-packed columns) was greater than by their free-living counterparts. Total carbohydrates and extracellular polysaccharides, both normalized to cell protein, were greater (2.5- and 5-fold, respectively) for attached cells than for free-living cells. Also, adsorption of a polyanion-binding dye to the exopolymer fraction was sixfold greater for attached cells than for unattached cells. When surface-grown cells were resuspended in fresh medium, exopolymer production decreased to the level characteristic of unattached cells, which ruled out the possibility that attached cells comprised a subpopulation of sticky mucoid variants. The mechanism by which attachment stimulated exopolymer synthesis did not involve changes of the specific growth rate, growth stage, or limiting nutrient.

Attachment Stimulates Exopolysaccharide Synthesis by a Bacterium

Columns were packed with clean quartz sand, sterilized, and inoculated with different strains of bacteria, which multiplied within the sand at the expense of a continuous supply of fresh nutrient medium. The saturated hydraulic conductivity (HCsat) of the sand was monitored over time. Among the four bacterial strains tested, one formed a capsule, one produced slime layers, and two did not produce any detectable exopolymers. The last two strains were nonmucoid variants of the first two. Only one strain, the slime producer, had a large impact on the HCsat. The production of exopolymers had no effect on either cell multiplication within or movement through the sand columns. Therefore, the HCsat reduction observed with the slime producer was tentatively attributed to the obstruction of flow channels with slime. Compared with the results with Arthrobacter sp. strain AK19 used in a previous study, there was a 100-fold increase in detachment from the solid substratum and movement through the sand of the strains used in this study. All strains induced severe clogging when they colonized the inlet chamber of the columns. Under these conditions, the inlet end was covered by a confluent mat with an extremely low HCsat.

Effect of bacterial extracellular polymers on the saturated hydraulic conductivity of sand columns

(1976). Volatile Organic Compounds and Microorganisms. CRC Critical Reviews in Microbiology: Vol. 4, No. 4, pp. 333-382.

Volatile organic compounds and microorganisms.

Previous studies have shown that various microorganisms can enhance the dissolution of silicate minerals at low ( 8) pH. However, it was not known if they can have an effect at near-neutral pH. Almost half of 17 isolates examined in this study stimulated bytownite dissolution at near-neutral pH while in a resting state in buffered glucose. Most of the isolates found to stimulate dissolution also oxidized glucose to gluconic acid. More detailed analysis with one of these isolates suggested that this partial oxidation was the predominant, if not sole, mechanism of enhanced dissolution. Enhanced dissolution did not require direct contact between the dissolving mineral and the bacteria. Gluconate-promoted dissolution was also observed with other silicate minerals such as albite, quartz, and kaolinite.

Enhanced Dissolution of Silicate Minerals by Bacteria at Near-Neutral pH

Fifteen bacterial strains and four molds capable of growth on n-butane were isolated and partially classified The bacteria were mostly Arthrobacter sp and Brevibacterium sp; among the molds, Pen

Isolation and characterization of n-butane-utilizing microorganisms.

Intracellular structures were observed in two Arthrobacter spp. and in Candida utilis in media containing n-butane or 1-butanol as the sole source of carbon; these structures were absent in the sam...

Agnes C. Kormendy

Papers

Isolation and characterization of n-butane-utilizing microorganisms.

Characteristic cytoplasmic structures in microorganisms utilizing n-butane and l-butanol.