Efficient production of epsilon-poly-l-lysine from lignocellulosic hydrolysates via zeolite-based solid-state...

The production of epsilon-poly-l-lysine (ε-PL) in submerged fermentation (SmF) exhibits defects of high energy consumption, excessive wastewater production, and inefficient oxygen transfer. To address these challenges, we developed an efficient ε-PL production method based on a novel solid-state fermentation (SSF) strategy using lignocellulosic hydrolysates as substrates and zeolites as solid carriers. The maximum ε-PL titer was found to be 47.6 g/L with spores inoculation at an initial pH of 6.5 and a 90 % medium saturation rate after 7 days of cultivation using an atomizing feeding system, representing a 1.88-fold increase of ε-PL productivity over conventional SmF. The increase in production can be attributed to elevated transcription of key genes, enhanced enzyme activity, increased energy metabolism, and enriched precursor pools, which were facilitated by direct oxygen transfer to cells, in situ removal of ε-PL and inhibitors, and reduced NH₄⁺ toxicity. This SSF approach offers a novel method for industrial-scale ε-PL biosynthesis.