Desenvolvimento de técnicas e avaliações de antimicrobianos visando a produção de etanol carburante
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Data
2016-02-04
Autores
Ventura, Ricardo [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A contaminação bacteriana nas destilarias de etanol é um problema crônico que afeta o rendimento, na medida em que esses microrganismos competem pelo substrato a ser convertido em álcool pelas leveduras e liberam produtos indesejados no meio. A adição de ácido sulfúrico ao inóculo é a prática mais utilizada no controle dessas bactérias, contudo é uma substância de baixa eficácia, que também afeta a levedura. Antibacterianos utilizados complementarmente devem levar em conta a seletividade; o espectro de ação; e ainda restrições em fermentações que utilizam o excedente de levedura para ração animal. Nesse contexto, esse trabalho se propôs a estudar diversos biocidas, com base na literatura e desempenho em outras áreas. Foram realizadas fermentações por bateladas em frascos agitados em condições operacionais padrão (pH, temperatura, concentração de açúcares) com recuperação de células ao final de cada ciclo, reproduzindo o processo industrial. Os inóculos contendo leveduras e bactérias foram tratados com os seguintes produtos: peróxido de hidrogênio aditivado com prata; cloro oxigenado; triclorocarbanilida; cloreto de benzalcônio; digluconato de clorexidina; maitenina; salinomicina, e agentes quelantes EDTA e HEDTA, além dos produtos referência (beta ácido de lúpulo e monensina). Ao final das fermentações foram analisadas a população de bactérias, a viabilidade da levedura, e os teores de ácido lático e etanol. O biocida a base de peróxido, na dose 1.000 ppm não mostrou a mesma eficácia registrada nos testes preliminares in vitro, que apontaram CIM de 200 ppm para bactérias láticas; os biocidas triclorocarbanilida (80 ppm) associado ao cloreto de benzalcônio e clorexidina (50 ppm) tiveram desempenho inferior ao reportado na literatura. O cloro oxigenado na dose 100 ppm afetou tanto a bactéria quanto a levedura. Os extratos vegetais (lúpulo e maitenina), dosado a 30 ppm, se mostraram inócuos à levedura, e exibiram efeito bacteriostático sobre bactérias. Os antibióticos ionóforos (monensina 3 ppm e salinomicina 6 ppm) foram os mais efetivos na inibição das bactérias, preservando a viabilidade e metabolismo da levedura, com maior produção de etanol. Os agentes quelantes na concentração 1.000 ppm não foram efetivos na desfloculação microbiana, nem aumentaram a produção de etanol.
Bacterial contamination in ethanol distilleries is a chronic problem that affecting the yield, once these microorganisms compete for the substrate to be converted to alcohol by yeast, as well as release undesired products in the medium. The addition of sulfuric acid to the inoculum is the most used practice to control such bacteria, but is a substance of low efficacy, which also affects the yeast. Antibacterial used in addition should take into account the selectivity; spectrum; and also restriction in fermentation that uses yeast surplus for animal feed. In this context, this work proposes to study various biocides, based on the literature and performance in other areas. Batch fermentations were performed in shake flasks under standard operational conditions (pH, temperature, sugar concentration) with a recovery of cells at the end of each cycle, reproducing the industrial process. The inoculum containing yeast and bacteria were treated with hydrogen peroxide plus silver; oxygenated chlorine; trichlorocarbanilide plus benzalkonium chloride; chlorhexidine digluconate; maytenin; salinomycin, and chelating agents EDTA and HEDTA, indeed the reference products (beta hops acid and monensin). At the end of fermentations were performed analysis of population of bacteria, yeast viability and lactic acid and ethanol concentration. The peroxide-based biocide in the dose 1000 ppm did not showed the same efficacy recorded in preliminary tests in vitro, which showed a MIC of 200 ppm for lactic acid bacteria; the trichlorocarbanilide biocides (80 ppm) associated with benzalkonium chloride and chlorhexidine (50 ppm) had underperformed reported in the literature. Oxygenated chlorine at dose 100 ppm affected both the bacterium as yeast. The plant extracts (hops and maytenin), dosed at 30 ppm, exhibited bacteriostatic effect on bacteria and proved harmless to yeast. Antibiotic ionophores (monensin - 3 ppm and salinomycin - 6 ppm) showed higher bactericidal effect, preserving the viability and metabolism of the yeast with increased ethanol production. Chelating agents at concentration 1000 ppm were not effective in microbial deflocculating and not increased ethanol production.
Bacterial contamination in ethanol distilleries is a chronic problem that affecting the yield, once these microorganisms compete for the substrate to be converted to alcohol by yeast, as well as release undesired products in the medium. The addition of sulfuric acid to the inoculum is the most used practice to control such bacteria, but is a substance of low efficacy, which also affects the yeast. Antibacterial used in addition should take into account the selectivity; spectrum; and also restriction in fermentation that uses yeast surplus for animal feed. In this context, this work proposes to study various biocides, based on the literature and performance in other areas. Batch fermentations were performed in shake flasks under standard operational conditions (pH, temperature, sugar concentration) with a recovery of cells at the end of each cycle, reproducing the industrial process. The inoculum containing yeast and bacteria were treated with hydrogen peroxide plus silver; oxygenated chlorine; trichlorocarbanilide plus benzalkonium chloride; chlorhexidine digluconate; maytenin; salinomycin, and chelating agents EDTA and HEDTA, indeed the reference products (beta hops acid and monensin). At the end of fermentations were performed analysis of population of bacteria, yeast viability and lactic acid and ethanol concentration. The peroxide-based biocide in the dose 1000 ppm did not showed the same efficacy recorded in preliminary tests in vitro, which showed a MIC of 200 ppm for lactic acid bacteria; the trichlorocarbanilide biocides (80 ppm) associated with benzalkonium chloride and chlorhexidine (50 ppm) had underperformed reported in the literature. Oxygenated chlorine at dose 100 ppm affected both the bacterium as yeast. The plant extracts (hops and maytenin), dosed at 30 ppm, exhibited bacteriostatic effect on bacteria and proved harmless to yeast. Antibiotic ionophores (monensin - 3 ppm and salinomycin - 6 ppm) showed higher bactericidal effect, preserving the viability and metabolism of the yeast with increased ethanol production. Chelating agents at concentration 1000 ppm were not effective in microbial deflocculating and not increased ethanol production.
Descrição
Palavras-chave
Fermentação etanólica, Contaminação bacteriana, Biocidas, Descontaminação de levedura, Tratamento de melaço, Ethanol fermentation, Bacterial contamination, Biocides, Yeast decontamination, Molasses treatment