Non-antibiotic feed additives production by Acremonium terricola solid-fermented Camellia oleifera meal

The Camellia oleifera meal (COM), a primary byproduct of oil-tea processing, often being discarded or used as a low-grade fertilizer due to its low value. The underutilization has become a significant bottleneck hindering the high-quality development of the oil-tea industry. In this study, the production of antibiotic-free feed additives through the solid-state fermentation of COM by Acremonium terricola was investigated. Our findings revealed that a saponin concentration of 5 mg/mL significantly enhanced the production of cordycepic acid (70.4 mg/g), ergosterol (3.32 mg/g), and chitin (110 mg/g) by A. terricola. This concentration also promoted chitin production and the activities of peroxidase (POD) and Na⁺/K⁺-ATPase, thereby maintaining cellular homeostasis and energy balance in A. terricola. Solid-state fermented rice bran (RB), wheat bran (WB), and desaponificated COM (containing 2.6 mg/100 g of tea saponin) were all found to be beneficial for increasing the production of cordycepic acid and ergosterol. The blend of COM, RB, and WB in the ratio of 15:65:20 was particularly advantageous for the production and accumulation of cordycepic acid and ergosterol, yielding 1.54 and 1.43 times, 1.27 and 1.37 times, and 1.98 and 5.52 times more than those produced by WB, RB, and COM alone, respectively.Meantime, the difference in contents of sugar and protein in A. terricola cultures (ATCs) using combination were not significant compared to RB and WB. These results indicated that COM can partially replace foodstuffs or food by-products to prepare antibiotic-free feed additives by A. terricola.