The aim of this research was to evaluate the nutritional characteristics of Aphanothece microscopica Nägeli microalgae developed in the effluent of parboiled rice. The biomass was biologically evaluated by rat growth, during 10 days for nitrogen balance studies and 28 days for blood analysis. The feeding of Aphanothece biomass diets resulted in a nitrogen balance of 1.42 g/rat/day, an apparent biological value of 73.33%, an apparent digestibility of 82.12%, an apparent net protein utilization of 60.21% and a net protein retention of 2.40. Significant differences between the glycemic indices of rats fed with the Aphanothece and those fed with the control diet were not observed. However, the total cholesterol levels in the plasma of rats fed the test diet proved to be significantly lower. These results suggest the use of A. microscopica Nägeli developed in parboiled rice effluent as a potential source of single-cell protein.