α-amylase (1,4-α-D-glucan glucanohydrolase, EC 3.2.1.1) production by thermophilic Bacillus sp strain SMIA-2 cultivated in liquid media containing soluble starch reached a maximum at 48h, with levels of 57U/ mL. Studies on the α-amylase characterization revealed that the optimum temperature for activity was 70ºC. The enzyme was stable for 2h at 50ºC, while at 60ºC, 70ºC and 90ºC, 4%, 13% and 38% of the original activities were lost, respectively. The optimum pH of the enzyme was 7.5. After incubation of crude enzyme solution for 24h at pH 7.5, a decrease of about 5% of its original activity was observed. The enzyme was strongly inhibited by Co 2+ , Cu 2+ and Ba 2+ , but less affected by Ca 2+ , Mg 2+ , Ni 2+ , Sr 2+ and Mn 2+. The enzyme in 1M and 5M NaCl solutions the enzyme retained 70% and 47% of the original activity after 24h of incubation at 4ºC, respectively.

The aim of this study was to evaluate the effect of dietary supplementation with the autochthonous probiotic bacteria Bacillus cereus on growth performance, haematological parameters and survival of tambaqui (Colossoma macropomum). Tambaqui fingerlings (0.94 ± 0.02 g) were fed for 120 days the following diets: basal (without probiotic) and three supplemented diets (4.2 × 10 4 , 3.9 × 10 6 and 3.3 × 10 8 CFU/ g). Growth performance and haematological parameters were evaluated every 30 days. Thereafter, fish were challenged against Aeromonas hydrophila and survival was evaluated. Probiotic B. cereus improved weight and length gains (p < 0.05), and increased neutrophils and thrombocyte counts (p < 0.05) in tambaqui supplemented with 3.9 × 10 6 CFU/g diet. Challenged fish fed unsupplemented diet presented the lowest survival rate (33.4%) while fish fed diets supplemented at 4.2 × 10 4 , 3.9 × 10 6 and 3.3 × 10 8 CFU/g B. cereus had 88.8%, 80.5% and 80.5% relative per cent survival respectively. These results demonstrated that B. cereus supplemented as probiotics to C. macropomum for 120 days improved physiological and haematological responses, leading to enhanced survival in this fish species. K E Y W O R D Samazon, bacterium, fish, haematology, nutrition, performance

An aerobic, thermophilic, xylanolytic bacterium was isolated from local soil. The results of 16S rRNA sequence comparisons indicated that the isolate was closely related to Bacillus caldoxylolyticus and Bacillus sp strain AK1. These organisms exhibited 94% levels of ribossomal DNA sequence homology. Studies on the xylanase characterisation from liquid cultures grown on beechwood xylan revealed that the enzyme retained 100% of activity for 2 hours at temperatures ranging from 30 to 50º C, while at 60, 70 and 100º C, 10%, 11% and 29% of the original activities were lost, respectively. The optimum pH of the enzyme was found to be between 6.5 and 7.0. After incubation of crude enzyme solution for 24 hours at 25º C and at pH 5.5 to 8.0, a decrease of about 12% of its original activity was observed.

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This study evaluated the growth and survival of Betta splendens larvae exposed to different salt concentrations (NaCl 0, 2, 4, 6 and 8 g L-1) and stocking densities (1, 5, 10 and 15 larvae L-1) during 20 days. A completely randomized design in a 5x4 factorial scheme with three replications was used, and the fish reared in static system. At the end of the experiment were evaluated the final weight, total length, group uniformity, specific growth rate and survival. Total larvae mortality was observed in treatments with 4, 6 and 8 g L-1, demonstrating the susceptibility of this specie for these concentrations. However, the salinized water with 2 g L-1 promotes longer larvae when fish were maintained in densities of 10 and 15 larvae L-1. Further, there were no interactions between the addition of salt and stocking density for the other parameters. However, beneficial effects of salinized water (2 g L-1) were observed as better growth performance and survival of larvae. Regarding the stocking density, apart from addition of salt, the larvae present best development at density of 5 larvae L-1. Therefore, the use of salinized water (2 g L-1) and stocking density of 5 larvae L-1 is recommended for the Betta splendens larviculture.