Marina L. R. Vairo

Influence of temperature, dilution rate and sugar concentration on the establishment of steady-state in continuous ethanol fermentation of molasses

Abstract Continuous ethanol fermentations of sugar-cane blackstrap molasses were carried out in a laboratory-scale stirred vessel, without aeration and with no cell recycle, at different temperatures (27, 32 and 37°C), dilution rates (0·03-0·15 h−1) and sugar concentrations (100–190 g litre−1). In all the experiments at 27°C the system attained a steady-state, even when the ethanol concentration in the fermenting medium was as high as 76·4 g litre−1. Steady-states were never reached at 37°C even at a relatively low ethanol concentration (33·0 g litre−1). At 32°C the system response depended on the values of the dilution rate and sugar concentration. In this last case, the steady-state region can be represented by a graph of D versus So by means of ‘iso-alcoholic’ curves.

Kinetics of amyl alcohol production during ethanol fermentation of blackstrap molasses

Abstract This paper reports results of studies on the effect of increasing amyl alcohol production on the kinetics and on the yield of ethanol fermentation with molasses as substrate. The production of amyl alcohols at concentrations of up to 1·0 g litre −1 did not affect the alcoholic fermentation. The amyl alcohol yields, calculated as a percentage of the theoretical production, were 66· 4% from l -leucine,57·3% from l -isoleucine, 55·7% from a mixture of l -leucine and l -isoleucine, and 36·1% from racemic leucine. Aeration did not affect the yield of amyl alcohols. When no amino acid was added to the mash, the kinetics of amyl alcohol production as well as the final amyl alcohol concentration depended mainly on the inoculum size. When 2·0 g litre −1 of l -leucine or of racemic leucine were added to the fermentation media, the initial stages of the kinetic patterns and the values of the maximum rate of amyl alcohol production were almost the same.

Adsorption of Methylene Blue as a Means of Determining Cell Concentration of Dead Bacteria in Suspensions

The uptake of methylene blue by dead bacterial cells follows physicochemical adsoprtion laws, whether the microorganism is Gram-positive or Gram-negative. This fact was observed with Sarcina lutea, Bacillus subtilis, Micrococcus flavus, Serratia marcescens, Eschericiha coli, Proteus vulgaris and Pseudomonas aeruginosa. The initial dye concentration was about 100 mg/lit, and the maximum dry cell concentration varied from 0.3 to 2.2 gm/lit. A new method is described for determining colorimetrically the total bacterial cell concentration, analogous to our published method for yeasts (J. Bact., 76, 251-5 1958).

Determination of the volume fraction of yeast cells in a sediment or in a suspension

SummaryA simple and precise method for the measurement of the volume fraction of cells in a sediment or in a suspension is described. Determinations carried out with yeast cells sediments obtained from completely fermented molasses mash lead to cells volume fraction values affected by a coefficient of variation equal to 1.9% and to a cell density equal to 1.115 g.ml−1.When the method was applied to cells suspensions the coefficient of variation of the cells volume fraction was 2.9% and the cell density was 1.120 g.ml−1.

Semicontinuous alcoholic fermentation of sugar cane blackstrap molasses by pressed yeast

SummaryA third degree polynomial equation correlates the fermentation time and the volume fraction of inoculum in semicontinuous ethanol fermentation of sugar cane blackstrap molasses by pressed yeast. The volume of the inoculum varied from 40% to 92% of the reactor working volume. The highest ethanol productivity was obtained when the volume of the inoculum was 58% of the working volume.

Semicontinuous ethanol fermentation of sugar cane blackstrap molasses by pressed yeast. II: Mathematical model

SummaryA mathematical model is proposed to explain the influence of the volume fraction of inoculum on the fermentation time and ethanol productivity in semicontinuous ethanol fermentation of sugar cane blackstrap molasses by pressed yeast.

Production of crystals by Rozites gonglyophora. II - Some properties of the crystals. Influence of the temperature and of the culture medium on the production of crystals

In a previous paper (BoRzANI, 1960) it was shown that Rozites gonglyophora cultivated in glucose agar, in banana solid medium, and in glucose broth with and without aeration, produces large quantities of crystals that remain between the hyphae: it was also shown that these crystals present some peculiar properties regarding solubility and high temperature resistance. This paper has the purpose to present the results obtained in experiments carried out in order to study the crystals produced by Rozites gonglyophora, and the influence of the temperature and of the cuRure medium on the production of crystals.

A simple differential fermentograph

The very simple differential fermentograph described in this report can give good comparative measures of the influence of several factors on the fermentation rate when gases are produced.