The present invention relates to a composition comprising at least 90 wt% of a β-lactam compound characterized in that it contains between 0.02 and 5 wt% ammonium chloride and/or a corresponding amount of the HCI salt of an organic amine.
The present invention relates to a method for the identification of one or more genes of a parent microbial strain capable of producing a β-lactam compound and to mutant microbial strains in which the identified genes have been the functionally inactivated which results an at least 10% higher concentration of the total β-lactam compounds in the culture medium compared to the parent microbial strain and/or an at least 10% higher concentration of the desired β-lactam compound in the culture medium compared to the parent microbial strain; and/or an at least 10% improved yield (β-lactam / consumed sugar); and/or an at least 5% improved yield in desired β-lactam compound compared to undesired/total beta-lactam compound; and/or an at least 10% decreased consumption of side-chain precursor