No abstract

A hidrólise enzimática do amido de mandioca para produção de xaropes de glucose foi avaliada usando alfa-amilase de Bacillus licheniformis e glucoamilase de Aspergillus níger. Também, uma mistura enzimática composta de α-amylase de Aspergillus kawachi e glucoamilase de Aspergillus níger foi testada. As condições da enzima para a hidrólise do amido foram otimizadas por um planejamento fatorial experimental (3 3 ×2) usando como variáveis a concentração do substrato, a relação enzima/ substrato e o tempo de reação. As condições ótimas de reação com 100 g de amido per L foram: α-amilase pH 5,0, 80 °C e 130,5 U g -1 de amido; glucoamilase pH 4,5, 70 °C e 81,5 U g -1 de amido. Adicionalmente, as condições ótimas da mistura enzimática foram pH 4,5, 46 °C e 16,4 U g -1 de amido. Finalmente, a produção de álcool usando xaropes de glucose a partir do amido hidrolisado enzimaticamente foi realizada usando uma cepa selvagem de Candida sp isolada do caldo de cana de açúcar, obtendo produtividades em etanol volumétrico em torno de 1,Enzymatic hydrolysis of cassava starch for producing glucose syrups was evaluated using alpha-amylase from Bacillus licheniformis and glucoamylase from Aspergillus niger. Moreover, an enzyme mixture of α-amylase from Aspergillus kawachi and glucoamylase from Aspergillus niger was tested. Enzyme conditions for starch hydrolysis were optimized by a factorial experimental design (3 3 ×2) using as variables substrate concentration, enzyme/substrate ratio and time reaction. Optimal enzyme reactions with 100 g of starch per L were: α-amylase at pH 5.0, 80 °C and enzyme dosage of 130.5 U g -1 of starch; and glucoamylase, pH 4.5, 70 °C and enzyme dosage of 81.5 U g -1 of starch. Additionally, optimal conditions for the enzymatic mixture were pH 4.5, 46 °C, and enzyme dosage of 16.4 U g -1 of starch. Finally, alcohol production using glucose syrups from enzymatically-hydrolyzed starch was carried out with a wild strain of Candida sp isolated from sugar cane juice, obtaining volumetric ethanol productivities around 1.8-3.2 g L -1 h -1 .

The changes that occur during olive fruit (Olea europaea arolensis) processing (high pH treatment and fermentation) in the pectic fractions and hemicelluloses B of the cell wall have been studied. The amount of neutral arabinans in the cell wall and the composition of this fraction did not change, but there was a great decrease in the molecular weight [from higher than 400 000 in unprocessed fruit (UF) to 70 000 in processed fruit (PF)]. The water-soluble acidic polysaccharides almost disappeared, losing mainly their galacturonic acid-rich portions. The most important change that occurred in the oxalate-soluble rhamnogalacturonans was a decrease in their degree of esterification (from 75.44% and 35.42% for the peaks in UF to 28.42% for the peak in PF). Their composition and molecular weight were not greatly affected by processing. The molecular weights of the main polysaccharide components of the hemicelluloses B (xyloglucans, galactoglucomannans, and arabinoxylans) decreased greatly, although their sugar compositions remained almost stable.

Heme is an essential molecule synthetized through a broadly conserved 8-step route that has been lost in trypanosomatid parasites. Interestingly, Leishmania reacquired by horizontal gene transfer from g-proteobacteria the genes coding for the last 3 enzymes of the pathway. Here we show that intracellular amastigotes of Leishmania major can scavenge heme precursors from the host cell to fulfill their heme requirements, demonstrating the functionality of this partial pathway. To dissect its role throughout the L. major life cycle, the significance of L. major ferrochelatase (LmFeCH), the terminal enzyme of the route, was evaluated. LmFeCH expression in a heterologous system demonstrated its activity. Knockout promastigotes lacking lmfech were not able to use the ferrochelatase substrate protoporphyrin IX as a source of heme. In vivo infection of Phlebotomus perniciosus with knockout promastigotes shows that LmFeCH is not required for their development in the sandfly. In contrast, the replication of intracellular amastigotes was hampered in vitro by the deletion of lmfech. However, LmFeCH 2/2 parasites produced disease in a cutaneous leishmaniasis murine model in a similar way as control parasites. Therefore, although L. major can synthesize de novo heme from macrophage precursors, this activity is dispensable being an unsuited target for leishmaniasis treatment.