Statistical optimization of alkaline protease production from Penicillium citrinum YL-1 under solid-state fermentation

Area of Science:

• Microbiology
• Enzymology
• Food Science

Background:

• Traditional Chinese fish sauce contains proteases from halotolerant and halophilic microorganisms.
• Microbial enzymes, particularly proteases, are crucial in food fermentation and processing.

Purpose of the Study:

• To isolate and identify protease-producing fungi from traditional Chinese fish sauce.
• To optimize alkaline protease production by the identified fungal strain using solid-state fermentation.

Main Methods:

• Isolation and morphological identification of 30 fungal strains from fish sauce.
• Identification of the protease-producing strain (YL-1) as Penicillium citrinum using ITS sequencing.
• Optimization of solid-state fermentation conditions (peptone, initial pH, moisture content) using Plackett-Burman and Box-Behnken designs.

Main Results:

• One fungal strain, Penicillium citrinum YL-1, was identified as a producer of alkaline protease.
• Maximal alkaline protease production reached 94.30 U/mL.
• Optimal conditions for production were determined as 35.5 g/L peptone, pH 7.73, and 136% moisture content (v/w).

Conclusions:

• This study reports the first isolation and identification of a protease-producing fungus from traditional Chinese fish sauce.
• Penicillium citrinum YL-1 is a promising source of alkaline protease.
• Optimized solid-state fermentation significantly enhanced alkaline protease yield.