In this study, a novel chitinase-producing bacterium Chitinibacter sp. GC72 was isolated and investigated for N -acetyl-D-glucosamine production from crayfish shell enzymatic degradation. A dimeric chitinase was purified, which had an optimal activity at a pH of 6.8 and 40 °C. The metal ions Al 3+ , Cu 2+ , and Zn 2+ inhibited the chitinase activity, whereas Ca 2+ , Mn 2+ , and Mg 2+ promoted the activity. The chitinase was active on p -NP-GlcNAc with apparent K m value of 152.83 μmol/L and V m value of 49.12 μmol/L min at 37 °C. Based on the hydrolysate formed, the chitinase was characterized as an exo-hydrolytic N -acetyl glucosaminidase. Furthermore, combined treatment of ultra-micro grinding and ultrasonic with direct enzymatic hydrolysis of crayfish shell for GlcNAc production was investigated, which resulted in 15.2 g of GlcNAc production from 100 g of crayfish shell following chitinase degradation for 36 h.
Fangfang Zhao,Yang Li,Caiming Li,Xiaofeng Ban,Zhengbiao Gu,Zhaofeng Li
Starch is crucial to gluten-free bread (GFB) quality. Amylolytic enzymes modified starch in situ during breadmaking , impacting the quality of both fresh and stored bread. Here, the breadmaking and storage properties of GFB with added endo-amylases, exo-amylases and debranching enzymes were compared. The results demonstrated that the addition of amylolytic enzymes, especially exo-amylases and debranching enzymes, facilitated interactions between the enzymatically modified starch segments and structural agents to improve the structure and texture of fresh GFB. Exo-type β-amylase produced lower crumb firming rate than endo-type α-amylase, although they produced similar retrogradation enthalpies and relative crystallinities . Maltooligosaccharide-forming enzymes with a non-strict endo-/exo-mode of cleavage and debranching enzymes markedly reduced the crumb firming rate and retrogradation enthalpy. Yet, maltooligosaccharide-forming enzymes produced a similar relative crystallinity as α-amylase, indicating that enzymes with endo-/exo-modes depended less on the reduction of starch recrystallization to retard crumb firming compared with debranching enzymes.
危险品化学品经营许可证（带存储）