UB - Artigos em revistas internacionais
Permanent URI for this collection
Browse
Browsing UB - Artigos em revistas internacionais by Subject "Agro-industrial wastes"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Characterization of thermophile xylanase produced by anoxybacillus sp. strain 3M in submerged fermentation using brewers’ spent grainPublication . Alves, Luís; Ladeira, S. A.; Paixão, Susana M.The main goal of this study was the characterization of the extremophile xylanases produced by by Anoxybacillus sp. strain 3M, a thermophilic bacterium isolated from terrestrial hot springs (temperature of 90°C) samples collected on S. Miguel, Azores, Portugal. In this context, several batch fermentations using different agro-industrial wastes as inducer substrates (BSG – Brewers’ spent grain, wheat straw, sugarcane bagasse, and corn cobs) were performed towards an optimal enzyme production. The results for xylanase production showed that the higher enzymatic levels were obtained in the growth medium containing 1% (w/v) BSG (1.34 U mL-1), indicating that the BSG was the best inducer substrate, but the xylanase activity was also observed when wheat straw (1.33 U mL-1), sugarcane bagasse (0.80 U mL-1), corn cobs (0.30 U mL-1) and commercial xylan (0.21 U mL-1) were used as inducers. The extracellular crude enzymatic extract produced by Anoxybacillus sp. 3M in optimized submerged fermentation with BSG, attaining a maximal xylanase activity of 1.41 U mL-1 (i.e. 5-fold higher than with xylan), was further characterized for its optimal temperature and pH and stability. The highest enzyme activity was observed at a temperature of 60ºC and pH 5.3, but the enzyme retained 100% of its original activity after 96 h at 60°C and pH 7.0 and it still maintained 46% activity after 28 days at the same conditions. At 60ºC, the enzyme also retained its activity for pH ranging from 7.0 to 10.5. In addition, a zymogram of native gel analysis of the different culture supernatants revealed the presence of an enzymatic complex with an apparent molecular weight ranging from 400-500 kDa. Further application of strain 3M enzymatic extract to commercial oat spelts xylan revealed the presence of xylose and xylooligosaccharides (XOS), mainly X2 and X3, in the hydrolyzates produced. So, the thermostable and alkalistable extracellular xylanases from Anoxybacillus sp. 3M are biocatalysts with high potential for the development of processes where lignocellulosics are converted to precursors for several biotechnological applications.
- Integrated conversion of agroindustrial residue with high pressure CO2 within the biorefinery conceptPublication . Morais, Ana Rita C.; Mata, Ana C.; Lukasik, Rafal M.Sustainable production of energy and other added-value products from biomass-derived polysaccharides is a key challenge of an efficient biorefinery facility. Most technologies for biomass processing are energy demanding and use significant amounts of chemicals and catalysts. The need to develop a process which is devoid of all these shortcomings associated with conventional processes is emphasized. A new approach is demonstrated for an integrated wheat straw biorefinery using a green technology, highpressure CO2–H2O, to produce oligosaccharides from hemicellulose fraction and to enhance the cellulose digestibility for the enzymatic hydrolysis. Over the range of reaction conditions (130, 215, 225 °C and 0 to 54 bar of CO2), CO2 adds value to the process by in situ formation of carbonic acid that leads to higher dissolution of hemicellulose into xylo-oligosaccharides and xylose and to the use of less energy in comparison with water-only technologies. Without an additional chemical catalyst, high-pressure CO2–H2O out performed hydrothermal reactions and gave much higher total sugars yield for wheat straw (as high as 84% in comparison with 67.4% with auto-hydrolysis at a 10 °C higher temperature). Apart from the results obtained for valorisation of hemicellulose fraction, both chemical and physical effects of CO2 coupled to enzymatic hydrolysis resulted in a glucan conversion to glucose yield of 82%, which consists of 26% improvement over those obtained during auto-hydrolysis. The influence of the high pressure reaction on the processed solid was examined by spectroscopic methods (namely Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy). The obtained results suggest that the high pressure CO2-based method is a very promising alternative technology allowing integrated biomass processing within the biorefinery concept.
- A novel β-xylosidase from Anoxybacillus sp. 3M towards an improved agro-industrial residues saccharificationPublication . Marcolongo, L.; La Cara, F.; Del Monaco, G.; Paixão, Susana M.; Alves, Luís; Ionata, E.; Marques, Isabel PaulaABSTRACT: An intracellular β-xylosidase (AbXyl), fromthe thermoalkaline Anoxybacillus sp. 3M,was purified and characterized. The homodimeric enzyme (140 kDa) was optimally active at 65 °C and pH 5.5, exhibited half life of 10 h at 60 °C, 78 and 88% residual activity after 24 h, at pH 4.5 and 8.0, respectively. Fe2+, Cu2+, Al3+, Ag+ and Hg2+inhibited the enzyme; the activity was moderately stimulated by SDS and not influenced by β-mercaptoethanol. In the presence of p-nitrophenyl-β-D-xylopyranoside, AbXyl exhibited Km of 0.19 mM, Kcat of 453.29 s−1, KcatKm−1 of 2322 s−1mMandwas moderately influenced by xylose (Ki 21.25mM). The enzyme hydrolyzed xylo-oligomers into xylose and catalyzed transxylosilation reactions also in presence of alcohols as acceptors, producing xylo-oligosaccharides and alkyl-xylosides. Finally AbXyl was applied towards a statistically optimized process of brewery's spent grain bioconversion, highlighting the important role of this biocatalyst in reaching high yields of fermentable sugars.