1 Subjects: “...levulinic acid...”

2 Subjects: “...5,6-dihydroxyindole-2-carboxylic acid...”

3 Subjects: “...acid extraction...”

4 Subjects: “...organic acids...”

5 Subjects: “...peroxyacetic acid...”

6 Subjects: “...fatty acid...”

7 Subjects: “...acid leaching...”

8 Subjects: “...Salix carboniferous solid acid catalysts...”

9 Subjects: “...amino acid...”

10 Subjects: “...itaconic acid...”

11 Subjects: “...sulfuric acid decomposition...”

12 Subjects: “...acidic hydrolysis...”

13 Subjects: “...amino acid content...”