Mycelial cultivation of Phellinus linteus using cheese-processing waste and optimization of bioconversion conditions

A medicinal mushroom, Phellinus linteus, was successfully cultivated using a cheese-processing waste, whey, and the optimal bioconversion conditions for the maximum mycelial growth rate was also estimated through solid-state cultivation experiments. Response surface analysis with a face-centered design (center point replication = 5) was applied to statistically approximate the simultaneous effects of the three variables, i.e., substrate concentration (10-30 g lactose l⁻¹), temperature (20-30°C), and pH (4-6), on the mycelial growth rate of P. linteus. The following is a partial cubic model where η is the mycelial growth rate (K(r)) and x(k) is the corresponding variable term (k = substrate concentration, temperature, and pH in order): η = -23.8 + 8.67 × 10⁻² x₁ + 1.48x₂ + 1.77x₃ + 8.00 × 10⁻⁴ x₁x₂ + 7.25 × 10⁻² x₁x₃ + 5.13 × 10⁻² x₂x₃ -1.28 × 10⁻² x₁² -3.18 × 10⁻² x²₂. -2.64 × 10⁻¹ x₃² -3.28 × 10⁻³ x₁x₂ x₃ + 4.68 × 10⁻⁴ x₁²x₂. The produced response surface model proved to be significant (r² > 0.99, P-value <0.0001, coefficient of variation <5%) to describe the explored space. Temperature was found to be the most significant factor of dominant effects on the mycelial growth rate, and other variables such as temperature², pH, pH², and (substrate concentration² × temperature) also showed significant effects on the model output. The maximum mycelial growth rate was predicted to be 2.80 mm d⁻¹ at 29.7 g lactose l⁻¹, 26.2°C, and pH 5. Our results proved a good potential of whey to serve as an alternative growth medium for cultivating P. linteus mycelia. This may provide another potential for managing this nutrient-rich waste in a cost-effective way.