Production of 5-aminolevulinic acid from hydrolysates of cassava residue and fish waste by engineered Bacillus cereus PT1

The economical production of 5-aminolevulinic acid (ALA) has recently received increasing attention for its extensive use in agriculture. In this study, a strain of Bacillus cereus PT1 could initially produce ALA at a titre of 251.72 mg/L by using a hydrolysate mixture of low-cost cassava residue and fish waste. The integration of endogenous hemA encoding glutamyl-tRNA reductase led to a 39.30% increase in ALA production. Moreover, improving cell permeability by deletion of the LytR-CpsA-Psr (LCP) family gene tagU led to a further increase of 59.73% in ALA production. Finally, the engineered strain B. cereus PT1-hemA-ΔtagU produced 2.62 g/L of ALA from the previously mentioned hydrolysate mixture in a 7-L bioreactor. In a pot experiment, foliar spray of the ALA produced by B. cereus PT1-hemA-ΔtagU from the hydrolysates increased salt tolerance of cucumber by improving chlorophyll content and catalase activity, while decreasing malondialdehyde content. Overall, this study demonstrated an economic way to produce ALA using a microbial platform and evidenced the potential of ALA in agricultural application.