Whey, a large-scale dairy industry by-product, can be converted into whey protein concentrate (WPC), providing a cost-effective nutrient-rich substrate for microbial fermentation. We investigated protease production by Aspergillus oryzae using WPC as the sole substrate in submerged fermentation. Following fermentation, the protease was purified sequentially from the crude extract by salting-out, which yielded a substantial purification factor (~39), and subsequent ion-exchange chromatography. The non-adsorbed chromatographic fraction showed the highest protease activity (92.6 U/mL) and revealed one main protein band ~45 kDa via SDS-PAGE. Enzyme characterization demonstrated activity across neutral-to-alkaline conditions, optimal at pH 9.0 and 37 °C, with stability maintained between 30 °C and 37 °C. The enzyme was classified as a serine protease based on strong inhibition by PMSF and SDS; its activity was also inhibited by Zn²⁺, Mg²⁺, and K⁺, but enhanced by Ca²⁺. This work validates WPC as an efficient substrate for protease production by A. oryzae and presents a promising strategy for valorizing industrial by-products through sustainable biotechnology.

Due to the scarcity of sustainable inputs for photosynthetic microorganisms’ biotechnology, the search for natural substrates such as coconut water has gained prominence. This by-product is a substrate rich in macro- and micronutrients, as well as endogenous phytohormones that support microbial growth. In this context, this study aimed to use it as an alternative cultivation medium for Limnospira platensis (Gomont), formerly known as Arthrospira platensis, a high-value cyanobacterium. We evaluated growth parameters, phycocyanin concentration, purity, and biomass yield cultivated in coconut water and in SAG_1x medium, a modified Zarrouk medium. Over 35 days of cultivation, both media efficiently supported cyanobacterial growth. In coconut water, the specific growth rate was 0.305 d⁻¹, the maximum growth rate was 0.629 d⁻¹, and the productivity was 0.256 g L⁻¹ d⁻¹. In SAG_1x medium, the values obtained were 0.240 d⁻¹, 0.676 d⁻¹, and 0.218 g L⁻¹ d⁻¹, respectively. Phycocyanin obtained from cultivation in SAG_1x medium presented food-grade purity (OD620/OD280 ratio > 0.7), while in coconut water, it was 0.6. The pigment concentration and yield in SAG_1x (19.1 mg/L and 34.3%, respectively) also slightly exceeded those obtained with coconut water (14.3 mg/L and 25.5%, respectively). Despite this, the data reinforce the potential of coconut water as a viable and economically competitive alternative to conventional media for L. platensis production.

Background: Giardiasis remains a globally prevalent neglected parasitic disease, and limitations associated with conventional therapies highlight the need for alternative and complementary strategies. In this context, microalgae biocompounds have emerged as promising sources of antiparasitic agents. Objective: This study aims to evaluate the in vitro preliminary screening activity (vital dye exclusion). Methods: Aqueous extracts of Arthrospira platensis obtained by different extraction methods, as well as the bioactivity of the product derived from in vitro digestion (PDV), aiming to assess the influence of extraction and digestive bioactivation on antiparasitic efficacy. Extracts were produced by magnetic stirring and sonication, followed by exposure of Giardia duodenalis cysts to increasing concentrations, with metronidazole used as a reference drug. The PDV was generated using a standardized simulated gastrointestinal digestion model. Sonicated extracts showed enhanced membrane damage compared to mechanically stirred extracts, consistent with improved release of intracellular bioactive compounds. The IC ₅₀ values for the sonicated, agitated, and PDV samples were, respectively: 95,4; 153.1 and 43.6 μg/mL. Results: The PDV demonstrated activity across multiple concentrations and, under comparable conditions, outperformed metronidazole. These findings suggest that digestive processing may increase the bioaccessibility of active moieties responsible for antiparasitic effects. Conclusions: Overall, the results support A. platensis as a sustainable source of giardicidal biocompounds and highlight the relevance of physiologically relevant in vitro digestion models for predicting functional antiparasitic activity and guiding future translational research.