Lactic acid fermentation combined with chemical treatments is a new alternative to chemical extraction of by-products from organic wastes such as prawn and krill shells. This study investigated the potential of whole eggshells (WES) and eggshell membranes (ESM) fermentation to provide a multiproduct process, thereby eliminating waste and generating revenue. Dry WES and dry ESM were treated separately in a 2-L reactor using a glucose solution, with and without citric acid solution (CA) and commercial lactic acid bacteria as inoculants, to determine the protein and carbohydrate contents from the final products. Through this process, protein and calcium removal is achieved by enzymatic action on the tissues and by dissolving of calcium by organic acids, respectively. The best fermentation condition was obtained by including CA in the process. Mass balances from the WES and ESM treatments were carried out to identify the phases with major amount of protein, carbohydrate and calcium. In the WES treatments with/without CA, the liquid phase turned out to contain the major amount of protein (85.4 and 73.2%) from the final product. On the other hand, the solid phase turned out to contain mainly ash (80.47 and 80.49%), with high calcium content, from the final product. The high-solubility dialysed liquid phase (LP1) from the ESM treatment turned out to contain the major amount both of soluble protein (88.3%) and of exopolysaccharides expressed as carbohydrates (4.3%) and the low-solubility dialysed liquid phase (LP2) turned out to contain the major amount of insoluble protein (60.2%) from the final product. In addition, the first-precipitation solid phase (SP1) from the ESM treatment turned out to contain the major amount of ash (60.5%) from the final product. The foamy phase and the liquid phase from the WES treatment using CA were analysed by SDS-PAGE, two-dimensional electrophoresis and electrospray ionisation ion-trap mass spectrometry. Four proteins related to the hen eggshells were identified from these phases: chicken heat shock protein (Gallus gallus), glucose-regulated protein precursor, calcyclin and 60s acidic ribosomal protein p2 were identified in the liquid phase and a protein homologous with calmodulin, a ubiquitous intracellular Ca2+ receptor, was identified in the foamy phase. (c) 2006 Society of Chemical Industry.