Avaliação do resíduo da fermentação ABE (acetona-butanol-etanol) originado do aproveitamento da vinhaça etanólica
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Data
2017-11-17
Autores
Ferreira, Mariane Aparecida Messetti [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Diversos estudos tem avaliado a utilização da vinhaça em uma nova fermentação, visando a obtenção de sub-produtos. Nesta fermentação, chamada acetona-butanol-etanol (ABE), bactérias anaeróbias do gênero Clostridium podem converter matéria orgânica presente na vinhaça em acetona, butanol, etanol e ácidos orgânicos, que são recuperados do caldo fermentado mediante técnicas de separação. Após a recuperação dos produtos de interesse e da biomassa bacteriana, o resíduo final é descartado. Este resíduo, denominado vinhaça FA (vinhaça da fermentação anaeróbia) foi o objeto de estudo deste trabalho, bem como o processo fermentativo para a sua obtenção. Desse modo, o objetivo deste trabalho foi avaliar a vinhaça FA com relação às suas características físico-químicas e microbiológicas, bem como avaliar sua biodegradação em solo e sua toxicidade. Além disso, realizou-se fermentação utilizando-se cultura mista anaeróbia em meio de cultura sintético (MCS) suplementado com vinhaça e melaço. Avaliou-se a produção de ácidos orgânicos, acetona, butanol e etanol. A biodegradação da vinhaça FA em amostras de solo na presença e ausência de inóculo comercial foi avaliada mediante a produção de CO2 durante 57 dias. A quantificação de microrganismos foi realizada no início e no final do ensaio. Foram realizados ensaios de toxicidade aguda utilizando-se o microcrustáceo Daphnia similis; fitotoxicidade sobre Lactuca sativa e genotoxicidade ambiental com Allium cepa. A fermentação foi conduzida por 7 dias, sendo quantificados os teores de acetona, butanol e etanol por cromatografia gasosa, e ácidos orgânicos por CLAE, no início e final do ensaio. A vinhaça FA em solo atingiu 30% de eficiência de biodegradação após 13 dias. Não houve diferenças estatisticamente significativas com a adição de inóculo comercial. Vinhaça FA apresentou elevada toxicidade aguda para D. similis, com EC(50)= 9,10%; no entanto ensaios com o solubilizado mostraram que a toxicidade foi removida após o processo de biodegradação em solo. O crescimento relativo de L. sativa foi comprometido com o aumento da concentração de vinhaça FA, e a germinação foi inibida na concentração de 50%. Embora a vinhaça FA não tenha induzido efeitos genotóxicos e mutagênicos em A. cepa, a citoxicidade da amostra avaliada pelo índice mitótico foi dose dependente. As amostras mais concentradas (12 e 20%), apresentaram resultados estatisticamente significativos, interferindo no potencial citostático das células de A. cepa, levando a diminuição dos índices mitóticos e, consequentemente, decréscimo nos índices de germinação e de crescimento radicular. Os ensaios toxicológicos, permitem inferir que o descarte de vinhaça FA não deve ocorrer em rede hídrica, pois pode comprometer os organismos aquáticos; e para uso seguro como fertilizante agrícola, é indicado que esse resíduo passe por tratamento como a biodegradação, para que haja diminuição da sua toxicidade. Nos ensaios de fermentação anaeróbia realizados, não foram detectados acetona e butanol. Verificou-se produção de etanol de 2,32 e de 1,10 g/L nos ensaios contendo MCS suplementado com melaço e MCS suplementado com melaço e vinhaça, respectivamente. No ensaio contendo MCS suplementado somente com a vinhaça não houve produção de etanol. A suplementação com o melaço favoreceu a produção de ácido lático pela cultura mista, enquanto a produção de ácido butírico foi favorecida pela presença da vinhaça, atingindo valores de até 31,8 e 13,9 g/L, respectivamente.
Several studies have evaluated the use of stillage in a new fermentation in order to obtain by-products. In this fermentation, called acetone-butanol-ethanol (ABE), anaerobic bacterias of the genus Clostridium can convert organic matter present in the stillage in acetone, butanol, ethanol and organic acids which are recovered from the fermented broth by separation techniques. After recovering the interest products and bacterial biomass, the final residue is discarded. This residue, called AF stillage (stillage from anaerobic fermentation) was the object of study of this work, as well as the fermentation process to obtain it. Thus, the objective of this work was to evaluate AF stillage in relation to its physico-chemical and microbiological characteristics, as well as to evaluate its biodegradation in soil and its toxicity. In addition, fermentation was carried out using anaerobic mixed culture in synthetic culture medium (SCM) supplemented with stillage and molasses. The production of organic acids, acetone, butanol and ethanol was evaluated. The biodegradation of AF stillage was evaluated in soil samples in the presence and absence of commercial inoculum, through the production of CO2 for 57 days. Microorganisms quantification was performed at the beginning and at the end of the test. Acute toxicity tests using the microcrustacean Daphnia similis; phytotoxicity with Lactuca sativa and environmental genotoxicity with Allium cepa were performed. The fermentation was conducted for 7 days, and the contents of acetone, butanol and ethanol were determined by gas chromatography and organic acids by HPLC at the beginning and end of the test. AF stillage in soil reached 30% biodegradation efficiency after 13 days. There were no statistically significant differences with the addition of commercial inoculum. AF stillage presented high acute toxicity for D. similis, with CE(50) = 9.10%; however, the solubilized tests showed that the toxicity was removed after the soil biodegradation process. The relative growth of L. sativa was compromised with increasing AF stillage concentration, and germination was inhibited at 50%. Although AF stillage did not induce genotoxic and mutagenic effects in A. cepa, the cytotoxicity of the sample evaluated by the mitotic index was dose dependent. The most concentrated samples (12 and 20%) presented statistically significant results, interfering with the cytostatic potential of A.cepa cells, leading to a decrease in mitotic indexes and, consequently, a decrease in germination and root growth indexes. The toxicological tests, allow to infer that the disposal of AF stillage should not occur in water supply, as it may compromise aquatic organisms; and for safe use as agricultural fertilizer, it is indicated that such waste passes through treatment such as biodegradation to reduce its toxicity. In the anaerobic fermentation tests, acetone and butanol were not detected. There was an ethanol production of 2.32 and 1.10 g/L in the tests containing SCM supplemented with molasses and SCM supplemented with molasses and stillage, respectively. In the tests containing SCM supplemented with only stillage, there was not ethanol production. The supplementation with molasses favored the production of lactic acid by the mixed culture, while the production of butyric acid was favored by the presence of stillage, reaching values of up to 31.8 and 13.9 g/L, respectively.
Several studies have evaluated the use of stillage in a new fermentation in order to obtain by-products. In this fermentation, called acetone-butanol-ethanol (ABE), anaerobic bacterias of the genus Clostridium can convert organic matter present in the stillage in acetone, butanol, ethanol and organic acids which are recovered from the fermented broth by separation techniques. After recovering the interest products and bacterial biomass, the final residue is discarded. This residue, called AF stillage (stillage from anaerobic fermentation) was the object of study of this work, as well as the fermentation process to obtain it. Thus, the objective of this work was to evaluate AF stillage in relation to its physico-chemical and microbiological characteristics, as well as to evaluate its biodegradation in soil and its toxicity. In addition, fermentation was carried out using anaerobic mixed culture in synthetic culture medium (SCM) supplemented with stillage and molasses. The production of organic acids, acetone, butanol and ethanol was evaluated. The biodegradation of AF stillage was evaluated in soil samples in the presence and absence of commercial inoculum, through the production of CO2 for 57 days. Microorganisms quantification was performed at the beginning and at the end of the test. Acute toxicity tests using the microcrustacean Daphnia similis; phytotoxicity with Lactuca sativa and environmental genotoxicity with Allium cepa were performed. The fermentation was conducted for 7 days, and the contents of acetone, butanol and ethanol were determined by gas chromatography and organic acids by HPLC at the beginning and end of the test. AF stillage in soil reached 30% biodegradation efficiency after 13 days. There were no statistically significant differences with the addition of commercial inoculum. AF stillage presented high acute toxicity for D. similis, with CE(50) = 9.10%; however, the solubilized tests showed that the toxicity was removed after the soil biodegradation process. The relative growth of L. sativa was compromised with increasing AF stillage concentration, and germination was inhibited at 50%. Although AF stillage did not induce genotoxic and mutagenic effects in A. cepa, the cytotoxicity of the sample evaluated by the mitotic index was dose dependent. The most concentrated samples (12 and 20%) presented statistically significant results, interfering with the cytostatic potential of A.cepa cells, leading to a decrease in mitotic indexes and, consequently, a decrease in germination and root growth indexes. The toxicological tests, allow to infer that the disposal of AF stillage should not occur in water supply, as it may compromise aquatic organisms; and for safe use as agricultural fertilizer, it is indicated that such waste passes through treatment such as biodegradation to reduce its toxicity. In the anaerobic fermentation tests, acetone and butanol were not detected. There was an ethanol production of 2.32 and 1.10 g/L in the tests containing SCM supplemented with molasses and SCM supplemented with molasses and stillage, respectively. In the tests containing SCM supplemented with only stillage, there was not ethanol production. The supplementation with molasses favored the production of lactic acid by the mixed culture, while the production of butyric acid was favored by the presence of stillage, reaching values of up to 31.8 and 13.9 g/L, respectively.
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Palavras-chave
Biodegradação, Vinhaça, Fermentação anaeróbia, Toxicidade, Biodegradation, Vinasse, Stillage, Anaerobic fermentation, Toxicity