Browsing by Author "Pereira, Joana"
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- Ethanol production from enzymatically pretreated wheat strawPublication . Duarte, José Cardoso; Pereira, Joana; Paixão, Susana M.; Baeta-Hall, Lina; Ribeiro, Belina; Sàágua, M. C.Lignocellulosic biomass can be utilized to produce ethanol, a promising alternative energy source for the limited crude oil. Wheat straw is an abundant agricultural residue which can be used as lignocellulosic raw material for bioconversion. There are mainly two processes involved in the bioconversion: hydrolysis of cellulose in the lignocellulosic biomass to produce reducing sugars, and fermentation of the sugars to ethanol. The current study involved the optimization of enzymatic hydrolysis of a wheat straw pretreated by acid hydrolysis, using a mixture of commercial cellulases: celluclast 1.5L + Novozym 188, with further fermentation of the hydrolisate’ sugar content by three ethanologenic strains, namely two yeast of Saccharomyces cerevisiae (strains F and K) and a bacterial strain, Zymomonas mobilis (strain CP4). The fermentation assays, using undiluted hydrolisate with or without nutrient supplements, were monitored by the evaluation of glucose and ethanol yields. In the assays using no supplemented hydrolisate the results obtained for the two yeasts strains F and K, and Zymomonas mobilis were 74%, 79% and 58% of ethanol yield, respectively. However, when the hydrolisate was supplemented the fermentation results showed a better bioconversion process by the Z. mobilis, reaching 98% ethanol yield while the two strains of S. cerevisiae used maintained their behaviour. So, the fermentation results showed the necessity of the addition of nutrients for a good bioconversion process by the Z. mobilis, resulting in better ethanol yield than S. cerevisiae strains (F and K) from WSP hydrolisate.
- A multi-integrated approach on toxicity effects of engineered TiO2 nanoparticlesPublication . Picado, Ana; Paixão, Susana M.; Moita, Liliana; Silva, Luís; Diniz, M. S.; Lourenço, Joana; Peres, Isabel; Castro, Luísa; Correia, J.B.; Pereira, Joana; Ferreira, Isabel; Matos, A. Alves de; Barquinha, Pedro; Mendonça, E.The new properties of engineered nanoparticles drive the need for new knowledge on the safety, fate, behavior and biologic effects of these particles on organisms and ecosystems. Titanium dioxide nanoparticles have been used extensively for a wide range of applications, e.g, self-cleaning surface coatings, solar cells, water treatment agents, topical sunscreens. Within this scenario increased environmental exposure can be expected but data on the ecotoxicological evaluation of nanoparticles are still scarce. The main purpose of this work was the evaluation of effects of TiO2 nanoparticles in several organisms, covering different trophic levels, using a battery of aquatic assays. Using fish as a vertebrate model organism tissue histological and ultrastructural observations and the stress enzyme activity were also studied. TiO2 nanoparticles (Aeroxide® P25), two phase composition of anatase (65%) and rutile (35%) with an average particle size value of 27.6±11 nm were used. Results on the EC50 for the tested aquatic organisms showed toxicity for the bacteria, the algae and the crustacean, being the algae the most sensitive tested organism. The aquatic plant Lemna minor showed no effect on growth. The fish Carassius auratus showed no effect on a 21 day survival test, though at a biochemical level the cytosolic Glutathione-S-Transferase total activity, in intestines, showed a general significant decrease (p<0.05) after 14 days of exposure for all tested concentrations. The presence of TiO2 nanoparticles aggregates were observed in the intestine lumen but their internalization by intestine cells could not be confirmed.