The components were screened at the confidence level of 95% on the basis of their effects. If the component showed significance at or above 95% confidence level and its effect was negative, it indicated that the component was effective in lactic acid production but the amount required was lower than the indicated as low (−) concentration in Plackett–Burman experiment. If the effect was positive, a higher concentration than the indicated high value (+) concentration was required during further optimization studies.