Universidad Autonoma Metropolitana-Iztapalapa, Biotechnology Department, Laboratory of Biopolymers and Pilot Plant of Bioprocessing of Agro-Industrial and Food By-Products, Av. San Rafael Atlixco, No. 186, 09340, Mexico City, Mexico. Electronic address: [Email]
Chitins obtained by fermentation of shrimp wastes using Lactobacillus brevis with and without further inoculations with Rhizopus oligosporus resulted in higher molecular weight than the commercial biopolymer. After grinding in acidic conditions, the attained chitins were fully fibrillated by a mechanical treatment throughout ten passes in a high-pressure water jet system as evidenced by field-emission scanning electron microscopy. The chitin sample crystallinities decreased from 85% to 68%. A previous chitin sample bleaching, as well as the sonication of chitin nanofiber suspensions, enhanced the transparency in the resulting nanofiber sheets. Suspensions and sheets of chitin extracted by L. brevis with successive R. oligosporus inoculations displayed higher transmittance and acetylation degree, as well as improved mechanical properties compared to chitin extracted with only L. brevis. Mechanical studies demonstrated that Young's modulus of the nanofibers using this biological chitin was remarkably higher than that for the commercial product, an important characteristic in polymer reinforcements.