The present invention relates to a method for the production of a stable biodegradable, high water absorbable γ-polyglutamic acid (γ-PGA) hydrogel by directly cross-linking (A) a γ-polyglutamic acid (γ-PGA), a γ-polyglutamate, or a mixture thereof, and optionally a polysaccharide containing a carboxylic and/or carboxylate group, an amino acid, or a mixture thereof; and/or (B) a microbial culture broth containing a γ-polyglutamic acid (γ-PGA), a γ-polyglutamate, or a mixture thereof, and optionally a polysaccharide containing a carboxylic and/or carboxylate group, an amino acid, or a mixture thereof, with a cross-linker comprising a compound having three or more functional groups or a mixture of a compound having three or more functional groups and a compound having two functional groups, wherein each of the functional groups can react with a carboxylic group (—COOH), carboxylate group (—COO−), aldehyde group (—CHO), hydroxyl (—OH), carbonyl group (—CO), sulfone group (—SO2), amino group (—NH2) or nitro group (—NO2), or a mixture thereof. The present invention further relates to a stable biodegradable, high water absorbable γ-polyglutamic acid (γ-PGA) hydrogel and its uses.