Microalgae cell wall hydrolysis using snailase and mechanical sand milling

The extraction of intracellular constituents from recalcitrant microalgae strains stands as a significant challenge and a crucial bottleneck in microalgae processing. This study presents a novel enzymatic approach coupling mechanical lysis through sand milling without commercial glass or zirconium beads, with subsequent snailase treatment, resulting in improved cell wall breakdown and increased release of valuable constituents. The selected microalga was Chlorella sp. L06, renowned for its sturdy cell wall structure. Initial experiments involving sand milling unveiled substantial release of proteins (1.19 mg/mL) and chlorophyll (1.80 of absorbance at 680 nm), underscoring effective cell disruption. Remarkably, the application of snailase after sand milling produced noteworthy outcomes, fostering enhanced cell wall degradation and liberating a spectrum of constituents, encompassing soluble reducing sugars (1.13 mg/mL), proteins (2.28 mg/mL), and chlorophyll (2.83 of absorbance at 680 nm). The process was optimized by applying the Box-Behnken design, which revealed distinct operational parameters that significantly improved the release of soluble sugars and proteins by 46 % and 12.7 %, respectively. Moreover, the presence of snailase also showcased a protective antioxidant effect on chlorophyll during the hydrolysis, shedding light on its multifaceted role in the hydrolysis process. This study introduces an advantageous strategy for efficiently valorizing microalgae biomass using the synergistic potential of mechanical lysis and enzymatic treatment. Furthermore, the developed method contributes achieving promising, sustainable microalgae-based biorefineries.