Green and mild production of 5-aminolevulinic acid from algal biomass

Algal biomass was converted into 5-aminolevulinic acid (5-ALA) in five chemical steps: conversion to 5-(chloromethyl)furfural (5-CMF), ammoniation, ring-opening (photo-oxidation), reduction, and hydrolyzation. Among them, we mainly focused on the 5-CMF production and the following ammoniation. To our knowledge, the mixed solvent catalytic system of deep eutectic solvent (DES) and low concentration hydrochloric acid is the first reported for the synthesis of 5-CMF from algal biomass, providing a 24.6% 5-CMF yield at 120 °C for 5 h. Potassium phthalimide (KPI) was employed as an ammoniation reagent with superb selectivity and activity instead of conventional sodium azide (NaN3). Optimizing the experimental design, a 23.7% 5-ALA yield along with high purity (>96%) was achieved from 5-CMF, and the total 5-ALA yield was 5.8% from algal biomass. This work provides a green and mild pathway for 5-ALA production from algal biomass.