Combinatorial co-expression of xanthine dehydrogenase and chaperone XdhC from Acinetobacter baumannii and Rhodobacter capsulatus and their applications in decreasing purine content in food

This study investigated the combinatorial expression of xanthine dehydrogenase(XDH)and chaperone XdhC from Acinetobacter baumannii and Rhodobacter capsulatus and their applications in decreasing purine content in the beer,beef and yeast.Naturally occurring xdhABC gene clusters of A.baumannii CICC 10254 and R.capsulatus CGMCC 1.3366 as well as two refactored clusters constructed by exchanging their xdhC genes were overexpressed in Escherichia coli and purified to near homogeneity.RcXDH chaperoned by AbXdhC showed nearly the same catalytic performance as that by RcXdhC,except for the decreased substrate affinity.While the AbXDH co-expressed with RcXdhC displayed enhanced acidic adaptation but weakened catalytic activity.All the XDHs degraded purines in beer,beef and yeast extract effectively,indicating potential applications in low-purine foods to prevent hyperuricemia and gout.The study also presents a method for exploiting the better chaperone XdhC and novel XDHs by functional complement activity using existing XdhCs such as RcXdhC.

Screening and identification of purine degrading Lactobacillus fermentum9-4 from Chinese fermented rice-flour noodles

The aim of this study was to isolate a new purine-degrading potential probiotic strain from Chinese fermented rice-flour noodles and investigate its potential application in purine-degrading food development for promising anti-gout therapy.A new lactic acid bacteria strain designated as Lactobacillus fermentum 9-4 was screened out from 10 Shengzhamifen samples by a comprehensive method integrating agar plate selection,in vitro purine-metabolizing enzymatic activities of xanthine oxidase and urate oxidase,16 S rRNA gene sequencing and identification.The resting cells of L.fermentum 9-4 showed the maximum degradation rates of inosine and guanosine by respective 2.13×10^(-3) and 2.78×10^(-3) g/(L·min),and the highest assimilation ratio of guanosine by(55.93±3.12)%,which are improvements over LAB strains characterized previously.Yogurt fermented by L.fermentum 9-4 also efficiently assimilated the inosine and guanosine,with respective degradation rates of 98.10%and 98.56%higher than those of the commercial ones.The L.fermentum 9-4 showed excellent survival(>80%)under the conditions of pH 2.5 and 0.1%bile salt.The results suggest that L.fermentum 9-4 may be a promising candidate as a probiotic for developing low-purine foods.

Cross-species binding spectrum of ACE2 to SARS-CoV-2 RBD

Dear Editor,Severe acute respiratory syndrome coronavirus 2(SARSCo V-2)is the cause of COVID-19,which has posed a massive threat to human health,economy,and security worldwide(Bai et al.,2022).Genomic analysis of SARS-Co V-2 and related coronaviruses revealed that SARS-Co V and SARS-Co V-2likely had ancestors(Xu et al.,2020),which might originate in bats,followed by subsequent spread within intermediate hosts(spillover hosts)and then transmission to humans(Wang et al.,2021).

Chemical composition and pharmacological properties of Flos sophorae immaturus, Flos sophorae and Fructus sophorae: a review

The flower buds and fruits of Sophora japonica are known as Flos sophorae immaturus(Chinese Huaimi,FSI),Flos sophorae(Chinese Huaihua,FLS)and Fructus sophorae(Chinese Huaijiao,FRS)due to their different physiological forms.FSI and FLS are precious resources of homology of medicine and food,while FRS is a valuable Chinese herb,and all of which have been used for thousands of years.There are great differences in the active ingredients,functions and toxicological properties of FSI,FLS and FRS.However,they are often confused and assumed to have fairly similar validity,which is detrimental to their precision development of resources of homology of medicine and food.This review summarized the active constituents,analytical techniques and pharmacological properties of FSI,FLS and FRS,then systematically compared their differences.The article will help people better understand and distinguish the differences and characteristics of FSI,FLS and FRS in bioactive constituents,content of functional components and pharmacological properties,which can contribute to their highly efficient targeted applications in the future food and medical fields.

Complete genome sequence of Lactobacillus fermentum 9-4,a purine-degrading Lactobacillus probiotic isolated from Chinese fermented rice-flour noodles

Lactobacillus fermentum 9-4 is a purine-degrading probiotic firstly isolated from traditional fermented rice-flour noodles with special characteristics of southern China's Guangxi Zhuang Autonomous Region.L.fermentum 9-4 could efficiently reduce the purine contents in foods with excellent purine-nucleoside assimilation and purine-metabolizing enzymatic activities.Crude cell lysate of L.fermentum 9-4 showed strong purine degradation abilities on nucleosides including inosine,guanosine,and purines including xanthine and uric acid,indicating a complete purine metabolic pathway to degrade purine substances to allantoin.In this study,the whole genome of L.fermentum 9-4 was sequenced.Its genome consisted of a 2085632 bp circular chromosome without plasmid.The GC content of circular chromosome was 51.25%,including 2089 coding sequences(CDs),15 rRNA operons and 59 tRNA coding genes.Genetic analysis showed that at least 5 protein coding genes were related to purine lowering ability.In addition,neither toxic virulence factor nor drug resistance gene was identified by searching the virulence factor database and drug resistance gene database,suggesting good safety of L.fermentum 9-4.The results showed that L.fermentum 9-4 has a good potential for the development and utilization as a purine-degrading probiotic for low-purine foods.

Factors affecting selenium-enrichment efficiency,metabolic mechanisms and physiological functions of selenium-enriched lactic acid bacteria

Selenium(Se)-enriched lactic acid bacteria(LAB)are live bacteria preparations that accumulate and bio-transform inorganic Se into organic Se forms including Se-nanoparticles(SeNPs),Se-amino acids and selenoproteins.Se-enriched LAB can play the dual role of organic Se supplement and probiotic effects,and have great applications in the food and biomedical fields.Therefore,more and more attentions have been paid on the Se-enriched LAB.This paper firstly summarized the factors affecting the Se-enrichment efficiency of Se-enriched LAB,then discussed the metabolic mechanisms and physiological functions of Se-enriched LAB,and finally reviewed their applications in food production,in order to provide a guidance for the theoretical and practical implementation of Se-enriched LAB.We concluded that 1)both biomass and the amount of Se enrichment should be used as dual indicators to screen Se-enriched LAB and comprehensively optimize the influencing factors including initial Se concentration,pH,inoculation amount,species of LAB to ensure the Se enrichment efficiency.2)The metabolic mechanism underlining Se-enriched LAB needs to be further revealed,which will facilitate the production of higher value Se compounds by LAB.3)The proven physiological functions of Se-enriched LAB include 5 categories:antioxidant activity,antibacterial activity,improving the physical function of animals,detoxification and disease prevention.However,the application of Se-enriched LAB in medical field currently still lacks clinical research,and convincing clinical evidence of effectiveness for Se-enriched LAB on human being must be established.4)The application in the food field will benefit from the stable existence in the food system of Se-enriched LAB and public acceptance,which come before the various health benefits.In any case,the great potential value of Se-enriched LAB formulations deserves further comprehensive exploration and development.