Dilute acid pretreatment for enhancing the enzymatic saccharification of agroresidues using a Botrytis ricini endoglucanase

The enormous amount of agroindustrial residues generated in Brazil can be used as biomass to produce fermentable sugars. This study compared the pretreatments with different proportions of dilute acid. The method involved pretreatment with 0.5%, 1%, and 1.5% (v/v) sulfuric acid, followed by hydrolysis using the halotolerant and thermostable endoglucanase from Botrytis ricini URM 5627. The physicochemical characterization of plant biomass was performed using XRD, FTIR, and SEM. The pretreatment significantly increased the production of fermentable sugars following enzymatic saccharification from wheat bran, sugarcane bagasse, and rice husk: 153.67%, 91.98%, and 253.21% increment in sugar production; 36.39 mg⋅g^-1 ± 1.23, 39.55 mg⋅g^-1 ± 1.70, and 42.53 mg⋅g^-1 ± 7.61 mg⋅L^-1 of glucose; and 3.26 ± 0.35 mg⋅g^-1 , 3.61mg⋅g^-1 ± 0.74 and 3.59 mg⋅g^-1 ± 0.80 of fructose were produced, respectively. In conclusion, biomass should preferably be pretreated before the enzymatic saccharification using B. ricini URM 5627 endoglucanase.

Aplicação de óxidos de metais como catalisadores heterogêneos na isomerização da glicose em meio aquoso

RESUMO: Atualmente, o uso de fontes renováveis e sustentáveis para produzir energia e produtos químicos associados ao desenvolvimento de catalisadores heterogêneos é uma estratégia promissora, pois esses possuem a vantagem de serem recuperados e reutilizados, diminuindo custos e contaminações no produto. Nesse sentido, açúcares derivados de biomassa, como glicose e frutose, podem ser empregados como blocos de construção para fabricação de insumos químicos, que podem complementar ou substituir alguns derivados petroquímicos e que apresentam grande potencial industrial e alto valor agregado. Dessa forma, a isomerização da glicose à frutose em meio aquoso foi estudada utilizando óxidos de metais SnO2, MoO3 e SnO2/MoO3 comparativamente à reação sem catalisador. Foram avaliadas as atividades catalíticas em termos de conversão e rendimento à frutose nas temperaturas de 50 e 70º C com tempos de reação de 0,25 a 6 h. Os catalisadores foram caracterizados utilizando técnicas como espectroscopia de absorção na região do infravermelho (FTIR), análise termogravimétrica (TG/DTA) e difração de raio-X (DRX). Os resultados demonstram que o fator principal que influência a conversão da glicose são os sítios ácidos presentes nos sistemas catalíticos. Com esse estudo pode-se constatar que o óxido de molibdênio e o óxido misto conduziram a altas conversões, porém o óxido de molibdênio apresentou melhores resultados em termos de rendimento à frutose. Além disso, foram identificados e quantificados outros produtos minoritários como gliceraldeído e piruvaldeído. PALAVRAS-CHAVE: Biomassa. Catálise. Monossacarídeos.

Characterization of antimicrobial effect of organotin-based catalysts on diesel-biodiesel deteriogenic microorganisms

Organotin compounds are applied in several industrial reactions and can present antifungal and antibacterial activities. Incorrect handling and storage practices of biodiesel and diesel-biodiesel blends can lead to microbial development, impacting its final quality. Concerning this problem, this work investigated the antimicrobial action of two organotin catalysts used in biodiesel production with four isolated microroorganisms (Bacillus pumilus, Pseudomonas aeruginosa, Pseudallescheria boydii, and Aureobasidium pullulans) and a pool of microorganisms (ASTM E1259 standard practice). Samples of soybean biodiesel with different concentrations of dibutyl tin dilaurate (catalyst 1) and di-n-butyl-oxo-stannane (catalyst 2) were prepared and added of mineral medium. The pool of microorganisms was inoculated and incubated at 30 °C and final biomass was weighted after 14 days. Thereafter, soybean biodiesel with catalyst 2 was used. Fungal biomass was weighted, and plate count was used to assess bacterial growth. Results show that catalysts 1 and 2 presented no inhibitory activity on the pool of microorganisms evaluated. A slight inhibitory activity was observed for B. pumilus and A. pullulans growth, but not for P. boydii, P. aeruginosa, or the pool of microorganisms. All experiment exhibited acidification higher than sterile control. Infrared analysis show less microbiological degradation products in the tin-protected fuel with ASTM inoculum. These results suggest that these tin-based catalysts show no toxic effect on native microbial population and a slight effect on some isolated microbial population in laboratory scale and for the first time shows that these organotin compounds can be employed safely as biodiesel catalyst. Graphical abstract.

Stanosilicates based on Sn-magadiites applied in conversion of fructose at moderate temperatures

Sn-Magadiite stanosilicates were successfully synthesized by the hydrothermal method.

Synthesis and evaluation of the antibiotic and adjuvant antibiotic potential of organotin(IV) derivatives

A series of organotin(IV) derivatives was investigated in vitro for their antibiotic and adjuvant antibiotic properties (efflux pump inhibitors) against Staphylococcus aureus strains that overexpress efflux pump proteins for norfloxacin (SA-1199B), erythromycin (RN-4220) and tetracycline (IS-58). Most organotin(IV) compounds showed significant antibacterial activity with small Minimum Inhibitory Concentration (MIC) values, some of which were close to 1.0μg/mL (3.1μM), but this feature was also associated with substantial cytotoxicity. Nevertheless, the cytotoxicity of these organotin(IV) compounds can be overcome when they are used as antibiotic adjuvants. Their remarkable adjuvant antibiotic properties allow potentiation of the action of tetracycline (against IS-58 strain) by up to 128-fold. This likely indicates that they can act as putative inhibitors of bacterial efflux pumps. These results reinforce organotin(IV) complexes as promising antibacterial agents, and many of these complexes, if associated with antibiotics, can act as potential adjuvant antibiotic candidates.

Organotin(iv) compounds with high catalytic activities and selectivities in the glycerolysis of triacylglycerides

Sn(iv) complexes, i.e., di-n-butyltin dichloride, n-butyltin trichloride, di-n-butyltin dilaurate, n-butyl stannoic acid, and di-n-butyl-oxo-stannane, were tested as catalysts for the glycerolysis of triacylglycerides (TAGs) to produce monoacylglycerols (MAGs) and diacylglycerols (DAGs).

Sn(iv)-based organometallics as catalysts for the production of fatty acid alkyl esters

This paper discusses mechanistic aspects and applications of organotin(iv) catalysts.

Fructose conversion in the presence of Sn(iv) catalysts exhibiting high selectivity to lactic acid

The catalytic performance of a series of Sn(iv)-based organometallic complexes in fructose conversion was studied under several reaction conditions, and the conversion, yields, and selectivity measurements of this transformation have been evaluated.

Studies of Terminalia catappa L. oil: characterization and biodiesel production

Since the biodiesel program has been started in Brazil, the investigation of alternative sources of triacylglycerides from species adapted at semi-arid lands became a very important task for Brazilian researchers. Thus we initiated studies with the fruits of the Terminalia catappa L (TC), popularly known in Brazil as "castanhola", evaluating selected properties and chemical composition of the oil, as well any potential application in biodiesel production. The oil was obtained from the kernels of the fruit, with yields around 49% (% mass). Also, its fatty acid composition was quite similar to that of conventional oils. The crude oil of the TC was transesterified, using a conventional catalyst and methanol to form biodiesel. The studied physicochemical properties of the TC biodiesel are in acceptable range for use as biodiesel in diesel engines.