Low-intensity ultrasound combines synergistically with Lacticaseibacillus paracasei fermentation to enhance chitin extraction from crab shells

The large amounts of chitin in crab shells can be extracted for use in food and biomedical industries. But the traditional chemical-based chitin extraction uses large amounts of acid and alkali, which are environmentally harmful. The current study explored lactic acid bacteria (Lacticaseibacillus paracasei) fermentation and low-intensity ultrasound combination for crab shells chitin extraction. Our results show that intermittent low-intensity ultrasound (0.167 W/cm2) treatment for 10 min at 8 h intervals enhances bacteria growth to improve decalcification by 16.72% and deproteinization by 33.45% and shortens the fermentation time of crab shells to 48 h. Scanning electron microscopy examination of the fermented chitin revealed that the decalcification and deproteinization were more efficient with this combined treatment, whereas nuclear magnetic resonance and infrared spectroscopy analyses show that the extracted chitin had alpha conformation. Collectively, low-intensity ultrasound could be leveraged together with L. paracasei fermentation to enhance chitin extraction from crab shells. •Kimchi-isolated L. paracasei can efficiently ferment crab shells to extract chitin.•Low-intensity ultrasound improves chitin extraction by L. paracasei fermentation.•Low-ultrasound treatment increases crab shells decalcification and deproteinization.•α-chitin is main product of ultrasound and L. paracasei fermentation of crab shells.