Biodegradation and toxicity of waste from anaerobic fermentation of stillage

Several studies have been carried out to produce biofuels by anaerobic digestion of stillage from ethanol fermentation. This type of process, known as ABE Fermentation, generates by-products such as acetone, butanol and ethanol. This fermentation can use pure or mixed cultures of anaerobic bacteria, mainly of the genus Clostridium. In this context, there is the need for deeper studies for proper disposal of the residue resulting from Anaerobic Fermentation of ethanolic stillage, hereinafter referred to as AF stillage (stillage from Anaerobic Fermentation), obtained after this fermentation. Thus, the aim of this study was to evaluate the biodegradation and toxicity of stillage from Anaerobic Fermentation. The biodegradation of AF stillage in soil samples in the presence and absence of commercial inoculum was evaluated using a respirometric method described by Bartha & Pramer, according to the standard NBR 14283 (ABNT, 1999). The production of CO2 was evaluated for 57 days. Additionally, quantification of microorganisms was carried out at the beginning and end of the experiment. Toxicity tests were performed with the microcrustacean Daphnia similis using raw AF stillage and leachate from the respirometry test, according to the standard NBR 12713 (ABNT, 2009). The results of the respirometry test showed that, after 13 days of incubation, the biodegradation efficiency of all samples was above 30%. Using the Friedman statistical test, results showed that adding the inoculum caused no statistically significant difference in the biodegradation of AF stillage. The acute toxicity tests were performed on raw AF stillage and on the leachates showed that toxicity was removed after biodegradation in soil at all concentrations used. Thus, discharge of AF stillage into soil is an alternative viable disposal.16371863187

Effect of vinasse in biological production of alcohols and volatile organic acids by microbial consortium

Orientadores: Ariovaldo José da Silva, Bruna de Souza MoraesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia AgrícolaResumo: No Brasil, o efluente industrial produzido em maior quantidade é a vinhaça, caracterizada por altos níveis de ácidos orgânicos, fósforo, cálcio, potássio e magnésio. O reaproveitamento energético da vinhaça mostra-se como uma alternativa interessante para produção de biocombustíveis ou sub-produtos. Este trabalho avaliou o potencial da vinhaça como fonte de substrato e nutrientes para produção de álcoois e ácidos orgânicos voláteis (AOV) por meio fermentação em batelada utilizando consórcio anaeróbio (lodo de bovinocultura) pré-tratados com choque térmico (TT) e choque ácido-térmico (AT). Foram utilizados dois meios diferentes, de sacarose (S) e de vinhaça (V), sendo a sacarose a principal fonte de carbono. A vinhaça provou ser uma excelente fonte de nutrientes para os microrganismos envolvidos na fermentação butírica, uma vez que a adição de vinhaça melhora significativamente a produção de ácido butírico em comparação com meio de cultura sintético. As máximas concentrações de ácido butírico, iso-butírico e acético foram de 14,13 ± 0,77 g L-1 na amostra ATV B3; 10,34 ± 0,43 g L-1na amostra ATV B2 e; 4,13 ± 0,06 g L-1na amostra TTV B3, respectivamente. O rendimento dos AOV acético, iso-butírico e butírico e de etanol foi mais elevado nas amostras ATV B3 e TTV B3, atingindo valores máximos de 0,14; 0,28; 0,69 e; 0,26 g g-1 carboidratos totais, respectivamente. Não foram encontradas diferenças significativas entre métodos de pré-tratamento e enriquecimento de inóculo, AT e TT no que diz respeito a produção de ácido butírico e etanol. Em escala maior, operando em reator de 1,5 L, a fermentação de vinhaça bruta e melado de cana por consórcio microbiano AU mostrou potencial para produção de solventes como o butanol, uma vez que concentrações elevadas de ácido butírico foram produzidas, com concentração máxima, rendimento e produtividade de 13,85 g L-1; 0,64 g g-1 e; 199,98 mg L h-1, respectivamente. A caracterização microbiológica, pirosequenciamento, revelou a ocorrência em maior abundância de bactérias do gênero Clostridium, principalmente no consórcio AU e Lactobacillus mais abundante nos consórcios TT e AT. Foi identificada uma espécie conhecida pela produção de butanol, o C. pasteurianum no consórcio AU. Contudo, o presente trabalho representa um passo importante no desenvolvimento de um processo industrial para reutilização da vinhaça. A exploração de novos microrganismos e estudo dos fatores que interferem no processo de fermentação como pH, temperatura, nutrientes, densidade da cultura, cargas aplicadas e características do substrato, são fundamentais para o entendimento dos efeitos sinérgicos e antagônicos da associação de culturasAbstract: In Brazil, industrial waste produced in the greatest amount is vinasse, characterized by high levels of organic acids, phosphorus, calcium, potassium and magnesium. The energy reuse of vinasse shows up as an interesting alternative for the production of biofuels or byproducts. This study evaluated the potential of vinasse as a source of substrate and nutrients for the production of alcohols and volatile fatty acids (VFA) through fermentation batch using anaerobic consortium (cattle sludge) pre-treated with heat shock (TT) and acid-shock thermal (AT). We used two different media, sucrose (S) and vinasse (V), with sucrose being the main source of carbon. The vinasse proved to be an excellent source of nutrients for microorganisms involved in the butyric fermentation, since the addition of vinasse significantly improves the production of butyric acid as compared to synthetic culture medium. The maximum concentrations of butyric acid, iso-butyric and acetic acid were 14.13 ± 0.77 g L-1 in the sample ATV B3; 10.34 ± 0.43 g L-1 in ATV B2 and 4.13 ± 0.06 g L-1 in TTV B3, respectively. The yield of acetate, iso-butyric acid, butyrate and ethanol was higher in ATV B3 and TTV B3 samples, reaching maximum values of 0.14; 0.28; And 0.69; 0.26 g g-1 total carbohydrates, respectively. There were no significant differences between pretreatment and enrichment methods inoculum, TA and TT as regards the production of butyric acid and ethanol. On a larger scale, operating at 1.5 L reactor, crude fermentation vinasse and molasses of sugar cane from AU microbial consortium showed potential for producing butanol as the solvent, since high concentrations of butyric acid was produced, with maximum concentration, yield and productivity of 13.85 g L-1 0.64 g g-1 and 199.98 mg h L-1, respectively. Microbiological characterization, pyrosequencing, revealed the occurrence in greater abundance of the genus Clostridium bacteria, particularly the AU and most abundant Lactobacillus in consortium TT and AT consortia. C. pasteurianum, known for the production of butanol was identified in AU consortium. However, this study represents an important step in the development of an industrial process for reuse of vinasse. The exploration of new microorganisms and study of the factors that interfere in fermentation process such as pH, temperature, nutrients, cultures, applied loads and characteristics of the substrate are critical for understanding the synergistic and antagonistic effects of culture associatioMestradoAgua e SoloMestra em Engenharia Agrícol

Enriched microbial consortia for dark fermentation of sugarcane vinasse towards value-added short-chain organic acids and alcohol production

The role of sugarcane vinasse as a nutrient source and the impacts of different inoculum pretreatment methods (acid-thermal and thermal treatment) were assessed in acidogenic systems aiming to produce value-added short-chain organic acids (SCOA) and alcohols. In-depth microbiome characterization was also conducted by high-throughput sequencing of the 16S rRNA gene using the Miseq Illumina platform. SCOA production was 47.3 % higher in vinasse-fed reactors, with isobutyric (up to 10.3 g L−1) and butyric (up to 10.6 g L−1) acids as the primary metabolites most likely resulting from lactate conversion. Ethanol comprised the main product from solventogenic pathways in all conditions, with values ranging between 2.7 and 5.2 g L−1, whereas no butanol was detected. Microbial analyses revealed high relative abundance values for the Clostridium, Lactobacillus, Bacillus and Ruminococcus genera, with the predominance of the Clostridium genus (17%) in acid-thermal treatment reactors and the Lactobacillus genus (37%) in thermal treatment reactors. Overall, vinasse proved to be a suitable substrate for value-added SCOA production, which characterizes a potential management approach to this wastewater stream. In this sense, the biochemical production of butyrate from vinasse could diversify the product portfolio of sugarcane biorefineries, also minimizing bioenergy losses by converting residual carbon fractions1275594601FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2016/16438-3; 2012/09785-8The authors acknowledge Dr. Eloisa Pozzi and Dr. Isabel Kimiko Sakamoto (LPB/EESC/USP), who assisted in the DNA extraction step. This work was supported by the São Paulo Research Foundation (FAPESP) [grant numbers 2016/16438-3 and 2012/09785-8]. The authors declare no conflict of interes