Proteolytic, milk-clotting, and stability properties of proteases from Solanum elaeagnifolium fruit

Abstract

Solanum elaeagnifolium (trompillo) has been considered a new alternative source of proteolytic enzymes for cheese-making. However, properties for this proteolytic source still need to be described. This study evaluated the proteolytic (PA) and milk-clotting activity (MCA) as well the stability properties for the proteases found in S. elaeagnifolium fruit extract (FE). Proteolytic enzymes were active in a broad pH range with a maximum at pH 10.0 and 80 °C and showed high stability in a wide pH (5.0–12.0) and temperature ranges (30–75 °C). MCA increased with the temperature in a range of 30–85 °C. Proteases from S. elaeagnifolium FE presented high thermostability, retaining 40% of the activity after 15 min of incubation at 80 °C. Temperatures higher than 85 °C caused the total PA loss. Phenylmethylsulphonyl fluoride (PMSF) inhibited more than 95% of the PA, indicating that the activity is mainly related to serine proteases. In addition, a casein hydrolysis profile, by SDS-PAGE, showed that proteases degrade α, β, and κ-casein with high affinity. S. elaeagnifolium fruit contains abundant proteolytic enzymes with high catalytic properties and activity over different protein substrates. Therefore, S. elaeagnifolium fruit represents a potential source of serine proteases for use in different biotechnological processes, offering attractive properties such as high activity in a broad pH and temperature range, high thermal stability, and preference over different natural substrates.