A continuous process for casein production using high-pressure carbon dioxide

Scale-Up Technologies for the Manufacture of Adherent Cells

Great importance is being given to the impact our food supply chain and consumers' food habits are having on the environment, human health, and animal welfare. One of the latest developments aiming at positively changing the food ecosystem is represented by cultured meat. This form of cellular agriculture has the objective to generate slaughter-free meat products starting from the cultivation of few cells harvested from the animal tissue of interest. As a consequence, a large number of cells has to be generated at a reasonable cost. Just to give an idea of the scale, there were billions of cells just in a bite of the first cultured-meat burger. Thus, one of the major challenges faced by the scientists involved in this new ambitious and fascinating field, is how to efficiently scale-up cell manufacture. Considering the great potential presented by cultured meat, audiences from different backgrounds are very interested in this topic and eager to be informed of the challenges and possible solutions in this area. In light of this, we will provide an overview of the main existing bioprocessing technologies used to scale-up adherent cells at a small and large scale. Thus, giving a brief technical description of these bioprocesses, with the main associated advantages and disadvantages. Moreover, we will introduce an alternative solution we believe has the potential to revolutionize the way adherent cells are grown, helping cultured meat become a reality.

Fractionation of whey protein isolate with supercritical carbon dioxide to produce enriched α-lactalbumin and β-lactoglobulin food ingredients

An environmentally friendly protein fractionation process using supercritical carbon dioxide (SCO(2)) as an acid was developed to produce enriched α-lactalbumin (α-LA) and β-lactoglobulin (β-LG) fractions from whey protein isolate solutions containing from 2 to 10% WPI. This study investigated the effects of pH, temperature, WPI concentration, and residence time on the precipitation kinetics and recovery yields of individual whey proteins and the relative enrichment and composition of both protein fractions. At 5.5-34 MPa and 60-65 °C, solubilized SCO(2) decreased solution pH and induced the formation and precipitation of α-LA aggregates. Gel electrophoresis and HPLC of the enriched fractions demonstrated the production of ≥ 60% pure α-LA, and ≥ 70% pure β-LG, under various operating conditions, from WPI containing ∼57% β-LG and 21% α-LA. The enriched fractions are ready-to-use food ingredients with neutral pH, untainted by acids and contaminants.

Fractionation of whey protein isolate with supercritical carbon dioxide-process modeling and cost estimation

An economical and environmentally friendly whey protein fractionation process was developed using supercritical carbon dioxide (sCO(2)) as an acid to produce enriched fractions of α-lactalbumin (α-LA) and β-lactoglobulin (β-LG) from a commercial whey protein isolate (WPI) containing 20% α-LA and 55% β-LG, through selective precipitation of α-LA. Pilot-scale experiments were performed around the optimal parameter range (T = 60 to 65 °C, P = 8 to 31 MPa, C = 5 to 15% (w/w) WPI) to quantify the recovery rates of the individual proteins and the compositions of both fractions as a function of processing conditions. Mass balances were calculated in a process flow-sheet to design a large-scale, semi-continuous process model using SuperproDesigner® software. Total startup and production costs were estimated as a function of processing parameters, product yield and purity. Temperature, T, pressure, P, and concentration, C, showed conflicting effects on equipment costs and the individual precipitation rates of the two proteins, affecting the quantity, quality, and production cost of the fractions considerably. The highest α-LA purity, 61%, with 80% α-LA recovery in the solid fraction, was obtained at T = 60 °C, C = 5% WPI, P = 8.3 MPa, with a production cost of $8.65 per kilogram of WPI treated. The most profitable conditions resulted in 57%-pure α-LA, with 71% α-LA recovery in the solid fraction and 89% β-LG recovery in the soluble fraction, and production cost of $5.43 per kilogram of WPI treated at T = 62 °C, C = 10% WPI and P = 5.5 MPa. The two fractions are ready-to-use, new food ingredients with a pH of 6.7 and contain no residual acid or chemical contaminants.

Acceleration of precipitation formation in peach juice induced by high-pressure carbon dioxide

Peach juice was treated by high-pressure carbon dioxide (HPCD). HPCD-induced acceleration of precipitation formation in peach juice was observed. Particle size distribution (PSD), pH, zeta-potential, protein and total phenols, pectin methylesterase (PME) activity, pectin and calcium, and viscosity in juice, contributing to the precipitation formation, were studied. HPCD resulted in a significant alteration of juice PSD pattern; the acceleration of the precipitation formation concurred with this alteration. A significant decrease of protein and a declining trend of total phenols were obtained, the contents of pectin and calcium were not changed, and the difference in PME activity in juice was not significant after HPCD. HPCD led to higher increase in juice viscosity, whereas pH and the absolute value of zeta-potential declined during HPCD. These results suggested that the pH and absolute value of zeta-potential declines induced the coagulation of protein and decrease of particle charge, responsible for the acceleration of the precipitation formation.

Alterations in the activity and structure of pectin methylesterase treated by high pressure carbon dioxide

The influence of high pressure carbon dioxide (HPCD) on the activity and structure of pectin methylesterase (PME) from orange was investigated. The pressures were 8-30 MPa, temperature 55 degrees C and time 10 min. HPCD caused significant inactivation on PME, the lowest residual activity was about 9.3% at 30 MPa. The SDS-PAGE electrophoretic behavior of HPCD-treated PME was not altered, while changes in the secondary and tertiary structures were found. The beta-structure fraction in the secondary structure decreased and the fluorescence intensity increased as HPCD pressures were elevated. After 7-day storage at 4 degrees C, no alteration of its activity and no reversion of its beta-structure fraction were observed, while its fluorescence intensity further decreased.

Development of a continuous process to make casein films

A semicontinuous pilot plant process was developed to make films from calcium caseinate plasticized with glycerol. Calcium caseinate/glycerol solutions were wetted and spread on polyethylene or Mylar belts and were readily removed after forming films. A Meier rod was used to spread the solution onto the belt. Feed rates were 3.3 and 5 g/cm. The resulting films using the polyethylene belt had a tensile strength of 5 MPa and 30% elongation with thickness of 0.14 mm. When the glycerol concentration was adjusted, the process produced films with properties similar to those previously reported for a batch process. It is anticipated that this process will apply to other proteins.

Drying kinetics of calcium caseinate

Drying is a major component of the cost of making caseinate-based films. We determined the drying curves for making calcium caseinate/glycerol films at low and high relative humidity at 21-34 degrees C. The drying curves exhibited a very long constant rate period followed by a single falling rate period. Much of the drying was in the constant rate period and preceded the actual film formation. Normally, calcium caseinate solutions are dried from about 5% solids, but it was possible to start with a more concentrated solution, 10% solids, to avoid much of the constant rate period. The resulting films were equal to those prepared starting at high initial moisture. An estimate of the drying costs indicated it is much cheaper to start with the more concentrated solutions.

Fractionation of soybean proteins with pressurized carbon dioxide as a volatile electrolyte

Fractionation of specific proteins from plant material is a complex and involved science, yet pure protein extracts are in high demand by a wide range of food and pharmaceutical industries. In this study carbon dioxide has been used as a volatile electrolyte to isoelectrically precipitate two major protein constituents of soybean. Carbon dioxide was shown to be effective in purifying glycinin and beta-conglycinin in a three-step process as 95% and 80% concentrated fractions with precipitation yields of 28% and 21%, respectively. Recycling of the mixed precipitate of the intermediary step enables complete separation into the concentrated fractions. Fractionation acidity was precisely controlled by a simple modification of pressure. In addition, the occurrence of a pH overshoot was prevented at any point in the fractionation vessel, as the pH minimum was defined by its equilibrium relationship with carbon dioxide operating pressure. The removal of the glycinin precipitate was an important factor in the purification procedure. The yield of the individual concentrated glycinin and beta-conglycinin precipitate fractions was a function of carbon dioxide pressure, extract concentration and, to a much lesser extent, temperature.

Isoelectric precipitation of soybean protein using carbon dioxide as a volatile acid

A novel process is presented for the isoelectric precipitation of soy protein, using carbon dioxide as a volatile acid. By contacting a soy meal extract with pressurized carbon dioxide, the solution pH was decreased to the isoelectric region of the soy proteins. Complete precipitation of the precipitable soy proteins could be achieved for protein concentrations up to 40 g/l at pressures less than 50 bar. Isoelectric precipitation with a volatile acid enabled accurate control of the solution pH by pressure and eliminated the local pH overshoot, usual in conventional precipitation techniques. The advantage of the improved precipitation control was reflected by the morphology of the precipitate particles. Protein aggregates formed by CO2 were perfectly spherical whereas protein precipitated by sulfuric acid had an irregular morphology. The influence of process variables to control particle size is discussed.