Process for preparing ortho-aminobenzoic acid or an ortho-aminobenzoic acid derivative, comprising the steps: fermentation of a raw material which comprises at least one fermentable carbon-containing compound by using microorganisms of a species selected from the group consisting of Escherichia coli, Pseudomonas putida and Corynebacterium glutamicum, wherein an ortho-aminobenzoate- and/or ortho-aminobenzoic-acid-comprising fermentation broth is obtained; optional pretreatment of the fermentation broth obtained in step, comprising removal of the microorganism from the fermentation broth obtained in step without pH adjustment, wherein a microorganism-depleted fermentation broth is obtained, and/or decolouration of the fermentation broth obtained in step or, when carrying out step, of the microorganism-depleted fermentation broth obtained in step, without pH adjustment; one-step treatment of the fermentation broth obtained in step or step or step in a reactor with acid such that ortho-aminobenzoic acid is precipitated from the fermentation broth; isolation of the ortho-aminobenzoic acid precipitated in step, wherein mother liquor remains; optional further purification of the ortho-aminobenzoic acid gained in step, preferably by washing with water; optional further conversion of the ortho-aminobenzoic acid obtained in step or step to form an ortho-aminobenzoic acid derivative; wherein step is carried out such that seed crystals of ortho-aminobenzoic acid are present and the presence of the seed crystals is achieved such that the fermentation broth and the acid are added to a suspension of seed crystals that has been initially charged in the reactor, wherein the seed crystals initially charged in the suspension consist, to an extent of at least 90% based on the total mass of all seed crystals initially charged in the suspension, of the form I modification of the ortho-aminobenzoic acid, according to the nomenclature in Ojala, W. H., Etter, M. C., J. Am. Chem. Soc. 1992, 114, 10288 - 10293, and wherein an aminobenzoic acid derivative means a product which is obtained by further chemical conversion of aminobenzoic acid. fermentation of a raw material which comprises at least one fermentable carbon-containing compound by using microorganisms of a species selected from the group consisting of Escherichia coli, Pseudomonas putida and Corynebacterium glutamicum, wherein an ortho-aminobenzoate- and/or ortho-aminobenzoic-acid-comprising fermentation broth is obtained; optional pretreatment of the fermentation broth obtained in step, comprising removal of the microorganism from the fermentation broth obtained in step without pH adjustment, wherein a microorganism-depleted fermentation broth is obtained, and/or decolouration of the fermentation broth obtained in step or, when carrying out step, of the microorganism-depleted fermentation broth obtained in step, without pH adjustment; removal of the microorganism from the fermentation broth obtained in step without pH adjustment, wherein a microorganism-depleted fermentation broth is obtained, and/or decolouration of the fermentation broth obtained in step or, when carrying out step, of the microorganism-depleted fermentation broth obtained in step, without pH adjustment; one-step treatment of the fermentation broth obtained in step or step or step in a reactor with acid such that ortho-aminobenzoic acid is precipitated from the fermentation broth; isolation of the ortho-aminobenzoic acid precipitated in step, wherein mother liquor remains; optional further purification of the ortho-aminobenzoic acid gained in step, preferably by washing with water; optional further conversion of the ortho-aminobenzoic acid obtained in step or step to form an ortho-aminobenzoic acid derivative;