Chitosan (Ch) from biologically obtained chitin by lactic acid fermentation process was successfully grafted with lactic acid following three different procedures, direct d,l-lactic acid attachment with and without the aid of p-toluene sulfonic acid catalyst and by ring-opening of l-lactide. The produced materials behave as hydrogels responsive to pH changes and were characterized by X-ray diffraction analyses, swelling behavior, erosion, contact angle, and thermally. In addition, mechanical studies in films of the synthetized materials demonstrate that the increase in grafting improved the mechanical properties in terms of tensile strengths. All the grafted Chs showed inhibition of the pathogenic bacteria Pseudomonas aeruginosa, which corroborate the preservation of antimicrobial activities in the modified Ch. The study on cell attachment and viability of fibroblasts onto the grafted Ch films evidenced that regardless of the low mechanical improvement in the lowest incorporation of lactic acid (31%), it rendered the materials with the highest adherence and viability of fibroblasts. Nonetheless, lactic acid incorporation enhanced cell viability in all synthetized materials as compared to native Ch. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40252.