• Energy Research

This work investigated the efficiency of pressurized liquid extraction (PLE) and supercritical fluid extraction with cosolvent (SFE) in obtaining feijoa leaf extracts with high antioxidant and antibacterial activities. PLE was performed in customized equipment with environmentally friendly solvents, at 40/80 °C, in dynamic and static mode, and SFE was carried out for 210 min at 30 MPa, 55 °C and 15% ethanol-water as cosolvent. PLE extract (80 °C/ethanol-water/dynamic) provided the highest yield, total phenolic content, and antioxidant activities, but it was not effective as antibacterial agent. In contrast, SFE extract exhibited effectiveness against S. aureus, E. coli, and S. typhimurium, with minimum inhibitory concentration values from 14,211 to 3,553 µg.mL-1. Finally, gallic acid, catechin and isoquercetin were the major phenolics identified by liquid chromatography. Our findings revealed that feijoa leaf extracts by PLE and SFE have remarkable bioactivity, presenting a great potential to be used as natural food additives.

Simplex-centroid design along with artificial neural network coupled with genetic algorithm (ANN-GA) was applied to maximize exoglucanase production by Penicillium roqueforti ATCC 10110 under solid-state fermentation (SSF), using a blend of agroindustrial wastes as substrate. The first statistical treatment determined the ideal contents of green coconut shell, corn cob, and sugarcane bagasse in the substrate, which were 0.44, 2.06, and 2.50 g, respectively. The optimum conditions by the ANN-GA were obtained as follows: 24 h, 21 °C, and 8.1 and 81.0% for the time, temperature, pH, and moisture, respectively. Moreover, the predicted and the experimental values of exoglucanase activity were 267.94 and 268.58 IU/g, respectively. The optimization process increased the enzyme activity by up to 1263% compared with the preliminary analysis using individual substrates, demonstrating the high efficiency of the algorithms on predicting and optimizing enzyme production. Biochemical characterization demonstrated good thermostability, basic pH stability, halotolerance, and increased enzyme activity in the presence of metal ions (Co2+, Ca2+, Mg2+, and Fe2), solvents (ethanol and dichloromethane), and organic compounds (EDTA, Triton-X, and lactose,). These results indicate the algorithm efficiency for enzyme production purposes.