Enzymatic pre‐treatment of microalgae cells for enhanced extraction of proteins

Abstract

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 conventional techniques, including ultrasonication and high-pressure water extraction. Enzymatic pre-treatment was chosen as it could be carried out at mild shear conditions and does not subject the proteins to high temperatures, as with the ultrasonication approach. Using enzymatic pre-treatment, the extracted proteins yields of all tested microalgae strains were approximately 0.7 mg per mg of dry cell weight. These values were comparable to those achieved using a commercial lytic kit. Ultrasonication was not very effective for proteins extraction from Chlorella sp., and the extracted proteins yields did not exceed 0.4 mg per mg of dry cell weight. For other strains, similar yields were achieved by both treatment methods. The time-course effect of enzymatic incubation on the proteins extraction efficiency was more evident using laccase compared to lysozyme, which suggested that the former enzyme has a slower rate of cell disruption. The crude extracted proteins were fractionated using an ion exchange resin and were analyzed by the electrophoresis technique. They were further tested for their antioxidant activity, the highest of which was about 60% 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. Lysozyme was also found to enhance the extraction of pigments, with Chlorella sp. showing the highest pigments contents of 16.02, 4.59 and 5.22 mg/g of chlorophyll a, chlorophyll b and total carotenoids, respectively.

Apparent digestibility of nutrients, energy, essential amino acids and fatty acids of juvenile Atlantic salmon (Salmo salar L.) diets containing whole-cell or cell-ruptured Chlorella vulgaris meals at five dietary inclusion levels

“…In fact, one of the most commonly-used laboratory methods for microalgal cell wall rupture (e.g., sonication) was recently shown to be ineffective for protein extraction from Chlorella sp. (Al-Zuhair et al 2017). On the other hand, the processing used in the current study (e.g., freeze-drying followed by microfluidization) was effective at maintaining high protein quality based in vivo EAA digestibility for both the test diets and single ingredients for arginine (94-97%), histidine (85-96%), isoleucine (91-94%), leucine (92-95%), lysine (95-97%), methionine (92-96%), phenylalanine (90-95%), threonine (87-94%), tryptophan (83-98%) and valine (90-95%).…”

Effect of Enzymatic pre-treatment of microalgae extracts on their anti-tumor activity

“…in this work. The composition of the medium and the growth procedure are described in our previous paper [7] .…”

“…The methods of MA extraction were detailed in our previous paper [7] . Briefly, samples were extracted from 1 g wet harvested MA cells, which was mixed with 3.25 mL of 1 mg/mL lytic enzyme solution (lysozyme or cellulase) and 7.5 mL of 0.1 M phosphate buffer solution (PBS) of pH 7.00 and pH 5.00 for lysozyme and cellulase pre-treatments, respectively.…”

“…The disruption method must be effective in breaking up cell walls, but at the same time, it must protect the fragile proteins from denaturation. The effectiveness of using two enzymes, namely lysozyme and cellulase, for MA cell wall disruption and enhanced protein extraction was discussed in our previous paper [7] . Although we previously reported that lysozyme pretreatment was more effective in enhancing the extraction of proteins from MA, it is important to evaluate the effect of the treatment method on the anti-cancer bioactivity of the extracts, using various cancer and benign cell lines.…”

Carbohidratos y proteínas en microalgas: potenciales alimentos funcionales

“…Con este objetivo se utilizan varias técnicas, tal como recogen las investigaciones de Lee et al (2010), Onay et al (2016) y Suarez-García et al (2018 en las que se menciona el uso de la autoclave, microondas, sonicador, shock osmótico con solución salina, fresado con cuentas de zirconio o cristal, homogenización sobre hielo o la liofilización. Por otra parte, el uso de enzimas permite mejorar la extracción de proteínas en algunas especies de microalgas, tal como lo indica la investigación realizada por Al-Zuhair et al (2017), aunque el uso de fresado con cuentas es el método preferido a nivel industrial gracias a la posibilidad de usar grandes cargas de biomasa y la alta eficiencia de disrupción. Otras tecnologías se encuentran aún en desarrollo como son la micro fluidización, tecnología de arco pulsado, membranas cubiertas de polímero catiónico o la descompresión explosiva, que entre sus ventajas se cuentan el uso de temperaturas medias, que no necesitan usar solventes o ser amigables con el ambiente.…”