Poly(ε-L-lysine) and poly(L-diaminopropionic acid) co-produced from spent mushroom substrate fermentation: potential use as food preservatives

Poly(ε-L-lysine) and poly(L-diaminopropionic acid) are valuable homopoly (amino acids) with antimicrobial properties and mainly produced in submerged fermentation. In this study, we investigated their co-production using waste biomass and spent mushroom substrate in solid-state fermentation. Simultaneous production of poly(L-diaminopropionic acid) and poly(ε-L-lysine) was achieved in a single fermentation process using pearl oyster mushroom residues as substrate, with the supplement of glycerol and corn steep liquor. After optimization of the fermentation parameters, the maximum yield of poly(ε-L-lysine) and poly(L-diaminopropionic acid) reached 51.4 mg/g substrate and 25.4 mg/g substrate, respectively. The optimal fermentation conditions were 70% initial moisture content, pH of 6.5, 30°C and an inoculum size of 14%. Furthermore, the fermentation time was reduced from 8 days to 6 days using repeated-batch solid-state fermentation. Finally, the antimicrobial effects of poly(L-diaminopropionic acid) and poly(ε-L-lysine) were evaluated in freshly pressed grape juice, which indicated tremendous potential of this mixture in its use as biological preservative.

聚ε-赖氨酸（poly(ε-L-lysine)）与聚L-二氨基丙酸（poly(L-diaminopropionic acid)）是两类具备抗菌活性的高价值氨基酸均聚物，目前主要通过深层发酵工艺生产。本研究以废弃生物质与废弃蘑菇菌渣为底物，探究了二者的联合固态发酵生产方案。研究以珍珠牡蛎菇菌渣作为发酵底物，辅以甘油与玉米浆，在单一发酵流程中同步实现了聚L-二氨基丙酸与聚ε-赖氨酸的生产。经发酵参数优化后，聚ε-赖氨酸与聚L-二氨基丙酸的最高产量分别可达51.4 mg/g底物与25.4 mg/g底物。最优发酵条件为：初始含水率70%、pH值6.5、发酵温度30℃、接种量14%。此外，采用重复分批固态发酵工艺可将发酵周期从8天缩短至6天。最后，本研究在鲜榨葡萄汁中评估了聚L-二氨基丙酸与聚ε-赖氨酸的抗菌效果，结果表明该混合聚合物作为生物防腐剂具备巨大应用潜力。