Combination of Mechanical/Physical Pretreatments with Trypsin or Pancreatin on Arthrospira platensis Protein Degradation

Abstract

Arthrospira platensis contains high protein content and quality, which makes it a promising feed source for livestock animals. However, this microalga presents a recalcitrant peptidoglycan cell wall, and its main proteins form protein-pigment complexes attached to the algal thylakoid membrane. The purpose of the present study was to evaluate the effect of mechanical/physical pretreatments (bead milling, extrusion, freeze-drying, heating, microwave and sonication) combined with commercial enzymes (trypsin or pancreatin) on the degradation of A. platensis proteins. Protein degradation was assessed through the quantification of total protein and protein fractions (18–26 kDa, 40–48 kDa and others) on SDS-PAGE gels and the evaluation of the coefficient of protein degradation (CPD). The results showed that no significant differences were found among treatments for CPD values, except for an increase related to 18–26 kDa protein (phycocyanin subunits) with extrusion combined with pancreatin. In addition, extrusion and microwave caused a decrease of total protein in algal supernatant probably due to a denaturation/aggregation and reduction of solubility. Overall, extrusion is a promising pretreatment for A. platensis cell wall disruption and protein bioaccessibility. Further studies could elucidate how the effect of extrusion on protein solubility affects the activity of peptidases on protein degradation.

Effects of high dietary inclusion of Arthrospira platensis, either extruded or supplemented with a super-dosing multi-enzyme mixture, on broiler growth performance and major meat quality parameters

“…Recent in vitro studies have provided additional clarity on the enzymatic hydrolysis of A. platensis proteins following extrusion. The research by Costa et al [ 17 ] has been particularly informative, demonstrating an enhanced breakdown of protein fractions within the 18 to 26 kDa range, identified as phycocyanin subunits [ 16 ], when extruded A. platensis is combined with commercial pancreatin. This finding is pivotal as it indicates that extrusion pre-treatment can lead to a more efficient enzymatic release of phycocyanin, a protein known for its nutritional and functional benefits.…”

“…However, a conundrum arises from these studies where extrusion, despite its benefits, also causes protein denaturation and aggregation. Costa et al [ 17 ] and Spínola et al [ 18 ] observed that these denatured proteins were often not detectable in the supernatant post-extrusion, suggesting a profound modification of their physical state. Such changes are attributed to the harsh conditions of high pressure and temperature inherent to the extrusion process, as documented in the structural studies of proteins by Ahmed et al [ 37 ] and Buecker et al [ 38 ].…”

“…The microalga extrusion was performed by Sparos company (Olhão, Algarve, Portugal), following detailed conditions: 340 mL of water addition per minute, at 34 bars and 118 °C for the last extrusion barrel. This procedure occurred from 3 to 7 s. Then, the algal pellets were dried for 8 and 10 min at 120 °C [ 17 , 18 ]. The porcine pancreatin extract encapsulated 350 FIP-U/g of protease, 6000 FIP-U/g of lipase, and 7500 FIP-U/g of amylase.…”

“…However, the bioavailability of Spirulina’s nutrients, particularly proteins, is often limited by the algae’s indigestible cell wall and the stable protein-pigment complexes associated with its thylakoid membranes [ 16 ]. Advanced processing methods like extrusion have been suggested to disrupt these complexes, thereby enhancing protein digestibility [ 17 , 18 ]. Enzymatic treatment with peptidases, which catalyse the hydrolysis of peptide bonds in proteins [ 19 ], has been explored as a means to improve the bioaccessibility of Spirulina proteins [ 17 , 20 ].…”

“…Advanced processing methods like extrusion have been suggested to disrupt these complexes, thereby enhancing protein digestibility [ 17 , 18 ]. Enzymatic treatment with peptidases, which catalyse the hydrolysis of peptide bonds in proteins [ 19 ], has been explored as a means to improve the bioaccessibility of Spirulina proteins [ 17 , 20 ]. Moreover, these treatments have the potential to modulate gut viscosity by altering protein interactions, which could impact nutrient absorption in monogastric animals like poultry [ 21 , 22 ].…”