RESUMO

Bacterial nanocellulose (BNC) has attained elevated interest due to its versatile structure and high resistance characteristics. Accordingly, efforts have been made in order to reduce its production costs, such as the employment of its by-products as a nutrient broth to yield the microorganism. Residual brewer's yeast is an excellent recourse, due to its high nutritional value and availability. Therefore, research which aimed to contribute to the development of a low cost, efficient and biosustainable technology for BNC production with Gluconacetobacter hansenii was carried out. BNC was obtained from residual brewer's yeast hydrolysate at pH 7.0 and five days of incubation at 30 °C in static culture. The hydrolysate was characterized by the amount of sugars, fatty acids, total proteins and ash content. Subsequently, BNC obtained was characterized in terms of yield, carbon conversion ratio, hydrodynamic size, crystallinity, morphology, Fourier-transform infrared spectroscopy, and surface analysis. Residual brewer's yeast hydrolysate proved to be efficient in BNC production via gluconeogenesis with consumption of alanine, threonine and glycerol, obtaining 1.9 times the yield of the chemically defined broth adopted as standard. Additionally, properties observed in the obtained BNC were equal to those obtained from conventional chemical medium. The research contributed to bacterial nanocellulose production using by-products from the brewing industry.

Assuntos

RESUMO

Water reuse in industrial processes has been an increasing need encouraged in recent years. However, as the streams are recycled, solutes accumulate, thus requiring purification techniques. Membrane processes (reverse osmosis and electrodialysis) have been implemented and in order to increase the reuse of water at its highest level, crystallization has been evaluated to remove salts from the concentrate produced and get a feasible disposal. Nevertheless, contaminants affect the crystallization performance, thus making the removal of residual organics important for both the efficiency of crystallization and the increase of water reuse. In this context, aiming at establishing a sustainable virtuous circle, bone char (0.5-1.4 mm particle size, mesoporous structure) was used to remove refractory organics from an electrodialysis concentrate effluent (C-EDR) from a Brazilian petroleum refinery, at a lab-scale, in a fixed-bed adsorption column. Bone char selectively and partially removed the refractory organics, a complex mixture of long-chain hydrocarbons, aromatic compounds, carboxylic acids, amines and amides. The maximum adsorption capacity increased with the increase in bed depth and reduction in flow rate. A maximum removal of 35.60 mg g-1 was achieved for the highest bed depth evaluated (12.9 cm). The breakthrough curves indicated that bone char could adsorb part of the organic compounds from the C-EDR. The scaling up was possible for the C/C0 ratios of 0.55, 0.60 and 0.65, providing a service time at about 16 days for 45% removal efficiency for typical real operational conditions used in the refinery.

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RESUMO

Ácidos graxos voláteis (AGV) são importantes compostos intermediários indicadores da digestão anaeróbia. Este artigo apresenta dados de validação de uma metodologia para análise de uma mistura de sete AGV (C1 a C5) em amostras ambientais por cromatografia líquida de alta eficiência (CLAE). Foi utilizada uma coluna de exclusão iônica a 55ºC, volume de injeção de 10 µL e fase móvel (0,01 mol.L-1 H2SO4) a 0,6 mL.min-1. Os critérios de validação foram: limites de detecção e de quantificação, que ficaram na faixa de 5,0 a 10 mg.L-1 e 15 a 30 mg.L-1, respectivamente; linearidade (comprovada para todos os ácidos); repetitividade e sensibilidade (muito boa para a maioria dos ácidos); efeito de matriz (efeito de supressão observado para o ácido isobutírico) e exatidão (85 a 104%). Sendo assim, as condições operacionais adotadas se mostraram válidas para a quantificação de AGV em efluentes de reatores anaeróbios.

Volatile fatty acids (VFA) are important intermediate compounds that somehow indicate the efficiency of anaerobic systems. This paper presents results of method validation for seven VFA (C1 to C5) analysis in environmental samples by high performance liquid chromatography (HPLC). It was used an ion exclusion column kept at 55ºC; injection volume of 10 μL and mobile phase (0.01 mol.L-1 H2SO4) at 0.6 mL.min-1. The validation criteria adopted were: limits of detection and quantification, that fell in the ranges of 5.0 -10 mg.L-1 and 15-30 mg.L-1, respectively; linearity (verified for all acids); repeatability and sensibility (very good for most acids); matrix effect (suppression effect observed for isobutyric acid) and accuracy (from 85 to 104%). Therefore, the operational conditions adopted seemed to be adequate and valid to measure VFA in samples from anaerobic reactors.