Shrimp waste is the most important chitin source for commercial use. In this study chitin and chitosan were extracted from Penaeus semisulcatus waste collected from a shrimp processing landing center situated at Persian Gulf in south of Iran by chemical and microbial methods. Chitin and chitosan were extracted by alkali-acid treatment and the yields were 510 and 410mg/g, respectively. Demineralization is an important step in the chitin purification process from shrimp waste. Chemical extraction method included the use of NaOH solution and acetic acid. In microbial extraction, organic acids (lactic acid) produced by probiotic bacteria was used to demineralize microbial deproteinized shrimp shells. The study showed that the effectiveness of using lactic acid bacteria especially added Fe (NO₃)₃ as extra nitrogen source for demineralization of shrimp shells than chemical method (1750 against 810mg/g). Chitin and chitosan extracted from shrimp waste by chemical and microbial methods was crystalline powder, nonharmful and odorless, white and off-white, respectively. The moisture content was calculated as 63.8%. The amount of Ca, Fe, Cu and Mn present in the shells was 168, 35.58, 38.28 and 6.72mg/L, obtained by atomic absorption spectroscopy, respectively. The amount of calcium in the shells was 25 times higher than manganese. The results suggested Lactobacillus plantarum (PTTC 1058) is an attractive source of recovery for chitin and chitosan.