Susceptibility of Saccharomyces cerevisiae and lactic acid bacteria from the alcohol industry to several antimicrobial compounds

Abstract

The antimicrobial effect of several products including commercial formulations currently used in sugar and alcohol factories was determined by adapted MIC (Minimal Inhibitory Concentration) test on Saccharomyces cerevisiae and on natural contaminants Lactobacillus fermentum and Leuconostoc mesenteroides. The MIC test by macrodilution broth method was adapted by formulating of the culture medium with cane juice closely simulating industrial alcoholic fermentation must. Acid penicillin V (MIC 0.10-0.20 µg/ml) and clindamycin (MIC 0.05-0.40 µg/ml) were most effective against bacterial growth in 24 h. Among the chemicals, sulphite (MIC 10-40 µg/ml), nitrite (MIC <117 µg/ml) and copper sulphate (75-300 µg/ml) were the most effective. Zinc and manganese ethylene-bis-dithiocarbamate and dimethyldithiocarbamate did not show good inhibitory effect on bacteria (MIC > 50 µg/ml). Methyldithiocarbamate was efficient only on L. fermentum (MIC 2.5 µg/ ml) and S. cerevisiae (MIC 5.0 µg/ml). Thiocianate (MIC 1.2-5.0 µg/ml), bromophenate (MIC 9-18 µg/ml) and n-alkyldimethylbenzylammonium cloride (MIC 1-8 µg/ml) affected S. cerevisiae at similar inhibitory concentration for L. mesenteroides or L. fermentum. Formaldehyde was more effective on bacteria (MIC 11.5 -23 µg/ml) in both pH (4.5 and 6.5) than yeast (MIC 46-92 µg/ml). Several tested formulated biocides seriously affect S. cerevisiae growth in the similar dosages of the bacterial inhibition, so these products should be avoided or used only in special conditions for the bacterium control of fermentation process. For this step, the control of these contaminants by antibiotics are more suitable and effective.

Spittlebug impacts on sugarcane quality and ethanol production

“…High acidity and phenolics concentration in juice inhibit yeast metabolism and, therefore, compromise the conversion of sugars into ethanol (Polakovic et al, 1992;Narendranath et al, 2001). Reducing sugars were found in higher concentrations (p<0.01) in the cane harvested in October (0.89 and 2.08% in May/June and October, respectively).…”

“…These compounds can affect cane quality, as they are responsible for juice darkening, which results in low quality sugar, with high color levels (Godshall, 1999). Phenolics are also known to inhibit fermentation (Polakovic et al, 1992), directly affecting ethanol production (Ravaneli et al, 2006;Garcia et al, 2010). Ravaneli et al (2006) observed that the levels of total phenolics increased after spittlebug infestation Pesq.…”

“…This indicates that cane quality was probably the source of contamination. Infecting bacteria compete against yeasts for substrate, and consume sugar and ethanol, producing organic acids and gums, and reducing yeast viability and fermentation yield (Oliva-Neto & Yokoya, 2001). The results found in the present work indicate that spittlebug-damaged stalks were already under deterioration before the beginning of the fermentation cycles.…”

The Control of &lt;i&gt;Lactobacillus&lt;/i&gt; sp. by Extracellular Compound Produced by &lt;i&gt;Pseudomonas aeruginosa&lt;/i&gt; in the Fermentation Process of Fuel Ethanol Industry in Brazil

“…H 2 SO 4 showed medium flocculation, and this process occurred when the pH decreased [29]. Two factors should be involved, first the addition of sulphuric acid and a presence of Lactobacillus could decrease the pH until pH = 2.0 [30].…”

Uso De Antibióticos Convencionais E Antimicrobianos a Base De Lúpulo No Controle Da Infecção Bacteriana Em Fermentação Alcoólica

“…Ela pode causar consumo de açúcar, formação de goma, floculação do fermento, inibição de crescimento e queda da viabilidade das leveduras devido às toxinas e ácidos orgânicos excretados no meio, promovendo assim a redução no rendimento e na produtividade da fermentação (OLIVA-NETO;YOKOYA, 2001). …”