Chitin oligosaccharides for the food industry:production and applications

Chitin oligosaccharides(CHOS),high-value-added oligomers linked by N-acetyl-d-glucosamine(GlcNAc,NAG),and a small amount of d-glucosamine(GlcN,GA),have aroused increasing interest due to their excellent biological properties,including antibacterial,anti-inflammatory,and immunoprotective activities,and intestinal regulation.The efficient production and utilization of CHOS with high performance can solve problems from chitin as biowaste.However,the large-scale production of well-defined CHOS has not been fully accomplished due to the limited biotechnology and separation methods,thus impeding the research on their biological functions as well as their accurate applications.In this review,we comprehensively summarize the current preparation methods of CHOS,including the chemical,physical,enzymatic and biosynthetic methods.The advantages and disadvantages of the methods are discussed in terms of efficiency,economy,and environmental effects.Furthermore,the applications of CHOS in the food industry and their contributions to human health based on their excellent bioactivities are expounded.It is hoped that this review will help in providing new insights into the production of CHOS with high precision,and support the application of CHOS in serving the food industry as nutritional supplements or foods for special medical purposes.

Enhanced bioproduction of chitin in engineered Pichia pastoris

Biopolymer chitin and its derivatives have a wide range of applications in different fields.Chitin is primarily produced from marine crustacean by strong acid and strong alkali treatment.To reduce the environmental hazardous in the production of chitin,post-fermentation fungal biomass waste like fungi cell walls provides a viable alternative source for chitin.In this study,improved chitin content in yeast cell wall was achieved by overexpressing chitin biosyntheic pathway related genes.The chitin content was 51.5μg/mg cell wall and 122.9μg/mg cell wall in strain GS-1.10(gfat,uap and chs1 genes overexpression)and strain GS-2.6(gfat,gna1,agm1,uap and chs1 genes overexpression),which were 44.3%and 244.4%higher than that in control strain GS115,respectively.By overexpressing another chitin synthase gene(chs3),the chitin content in strain GS-3.10 was further increased to 136.2μg/mg cell wall,which was 10.8%and 281.6%higher than that in GS-2.6 and in control GS115,respectively.Moreover,chitin yield was further improved by various culture conditions optimization,and reached 162.4μg/mg cell wall,which was 4.43 times of that in the starting strain GS115.The final titer of chitin was 2.23 g/L culture broth in 84 h fed-batch fermentation in a 5 L bioreactor.To our knowledge,this is the first report of chitin production in engineered Pichia pastoris via biosynthetic pathway enhancement.

Cronobacter spp.,foodborne pathogens threatening neonates and infants

Cronobacter spp.(formerly Enterobacter sakazakii) are special foodborne pathogens. Cronobacter infection can cause necrotizing enterocolitis, sepsis and meningitis in all age groups, especially neonates and infants, with a high fatality of up to 80%, although the infection is rare. Outbreaks of Cronobacter infection are epidemiologically proven to be associated with contaminated powdered infant formula(PIF). Cronobacter spp.can resist dry environments and survive for a long period in food with low water activity. Therefore, Cronobacter spp.have become serious pathogens of neonates and infants, as well as in the dairy industry. In this review, we present the taxonomy, pathogenesis, resistance, detection and control of Cronobacter spp.