Production and stability of pigments by Talaromyces purpurogenus LC128689 in an alternating air phase-liquid phase cultivation system.

Effects of carbon source, nitrogen source, and alternatingly submerging the cells and exposing to gaseous oxygen on pigment production by Talaromyces purpurogenus LC128689, as well as pH, temperature, and UV stability of the pigments were investigated. Although fructose supported higher cell growth, a mixture of glucose and glycerol resulted in higher pigment production. Out of the organic and inorganic nitrogen sources investigated, peptone gave the highest cell concentration (7.2 ± 1.1 g/L) and pigment production (p ≤ 0 .05). The cells were then immobilized in loofa sponge and cultivated under alternating liquid phase-air phase (ALAP) system whereby the cells were alternatingly submerged and exposed to gaseous oxygen. After 20 days of cultivation, the concentrations of the red, orange, and yellow pigments were 30.15 AU500 nm , 15 AU460 nm , and 6.25 AU400 nm , respectively. In comparison with submerged culture in flasks, the red and orange pigments were 100% and 50% higher (p ≤ 0.05) in ALAP system. On the other hand, the yellow pigment was 100% higher in flask cultures than in ALAP. The three pigments were stable within a pH range of 2-12, retained more than 80% of their color intensity after autoclaving at (121°C and 1.0 atm) for 15 min and exposure to UV (3 uW/cm2 ) for 24 h.

Addition of Fillers to Sodium Alginate Solution Improves Stability and Immobilization Capacity of the Resulting Calcium Alginate Beads.

BACKGROUND: Although advantages of immobilization of cells through entrapment in calcium alginate gel beads have already been demonstrated, nevertheless, instability of the beads and the mass transfer limitations remain as the major challenges. OBJECTIVE: The objective of the present study was to increase the stability, porosity (reduce mass transfer limitation), and cell immobilization capacity of calcium alginate gel beads. MATERIALS AND METHODS: Sodium alginate was mixed with various concentrations of the starch or sugar and gelled in 2% calcium chloride solution. During the gelling and curing, the starch or sugar leached out of the beads and created micro-pores. RESULTS: Micro-porous beads prepared with starch were more stable and had higher immobilization capacity than those prepared with sugar. After 24 hours of incubation (curing) of the micro-porous beads prepared with starch in calcium alginate, the solubilization time in citrate buffer was 93 minutes compared to 41 minutes for the control beads (without starch). The compressive strength of the micro-porous beads was also higher (5.62 Mpa) than that of the control beads (5.54 Mpa). The optimal starch concentration for cell immobilization was 0.4%. With this starch concentration, the immobilized Bacillus subtilis and Saccharomyces cerevisiae cell densities were 5.6 × 109 and 1.2 × 108 cells/beads, respectively. These values were 36.5% and 74% higher than the value obtained for the control beads. This method of immobilization resulted in more uniform cell distribution. CONCLUSION: Addition of starch to the sodium alginate solution before gelation in calcium chloride solution increased the stability of the beads, increased the immobilized cell density, and resulted in a more uniform cell distribution in the beads.