(190ag) Antitumor and Antioxidant Activities of Crude Proteins Extracts from Enzymatically Treated Microalgae

Microalgae have been receiving a lot of attention as promising sources of lipids to be used mainly in biodiesel productions. Cultivating microalgae has a concurrent advantage of utilizing CO₂ as the sole carbon source, hence reducing harmful emissions, and they do not require the development of agricultural lands. The most important feature of microalgae is their ability to grow in saline water and at relatively high temperatures, which reduce freshwater loading and allow them to grown in desert climates. However, the interest in microalgae as sources of proteins, pigments and other high-value components has been much lower. The latter compounds however, may have a remarkable antioxidant and antitumor activities, which are more valuable than liquid fuels. In cancer treatment, natural bioactive compounds have less harmful side effects compared to their chemical alternatives.

For efficient protein extraction from microalgae, their rigid cell walls have to be disrupted, allowing the extraction solvent to reach and dissolve the proteins. The disruption method must be effective in breaking up cell walls, but at the same time, protect the fragile proteins from denaturation. Most commonly used cell disruption techniques, such as bead milling, ultrasonication, microwave radiation, cell homogenizer and high-pressure water, are either energy intensive or subject the extract to excessive heat and/or shear.

In this work, lytic enzymes, namely lysozyme and cellulose, have been suggested to be used instead, because they operate at milder shear conditions and do not subject the proteins to high temperatures. Crude proteins and pigments were extracted from different microalgae strains, both marine and freshwater. The effectiveness of enzymatic pre-treatment prior to protein extraction was evaluated and compared to a commercial lytic kit and ultrasonication. Using enzymatic pre-treatment, the extracted proteins yields of all tested microalgae strains were comparative to those

It was important to evaluate the effect of the treatment method on the anti-cancer bioactivity of the extracts. Therefore, the anti-cancer efficacies of dialyzed and undialyzed extracts were determined by measuring cell viability after treating four human cancer cell lines, specifically A549 (human lung carcinoma), MCF-7 (human breast adenocarcinoma), MDA MB-435 (human melanoma), and LNCap (human prostate cancer cells derived from a metastatic site in the lymph node). This was compared to the effects of the agents on the human BPH-1 cell line (benign human prostate epithelial cells). The t-test was used to statistically analyze the results and determine the significance. The aim of this work was to identify the microalgae that contains effective biochemical and chemical anti-cancer agents. It was important also to assess the effect of enzymatic disruption of cells walls on the anti-tumor activity of the extracts. The results of this work provide important information and could provide the foundation for further research to incorporate microalgae constituents into pharmaceutical anticancer therapeutic formulations.

It was found that the rate of cell disruption using laccase was faster than that of cellulsae. Against LNCap and A549 cells, the performance of cellulase-treated extracts was better than that of lysozyme-treated preparations, but they had similar effects against the other two tumor cell lines. The extracts from lysozyme-treated microalgae were found to be safer against the benign cells. After dialysis, the performance of the extracts from lysozyme-treated cells was enhanced significantly. The antioxidant activity of the extracted proteins was also tested, and the highest was found for the proteins from Nannochloropsis sp. The total phenolic contents in the selected strains were also determined, with Chlorella sp. showing the highest content reaching 17 mg g^-1. Lysozyme was also found to enhance the extraction of pigments, with Chlorella sp. showing the highest pigments contents.