Using response surface methodology optimize culture conditions for human lactoferrin production in desert Chlorella

To optimize the expression conditions for human lactoferrin production, we have constructed the transgenic chlorella with human lactoferrin named as GTD8A1-HLF, the original chlorella was separated from Gurbantunggut Desert in Xinjiang China. To further improve the production of human lactoferrin, a sequential methodology was used to optimize human lactoferrin production by GTD8A1-HLF. First, a screening trial using a Plackett-Burman design was done, and variables with statistically significant effects on human lactoferrin bio-production were identified. These were further optimized by central composite design experiments and response surface methodology. Finally, we found that the maximum human lactoferrin production (52.70 mg/L) was achieved under the following optimized conditions: Initial pH 5.0, NaNO3 concentration of 0.600 mol/L, FeSO4 concentration of 0.006 mol/L, and a CuSO4 concentration of 0.002 mol/L, with the other medium components constituting the basal culture medium BBM. The yield of HLF protein under optimized culture conditions was approximately 4-fold higher than that obtained by using the basal culture medium BBM. The findings are significant for the potential industrial use of GTD8A1-HLF.