Monitoring of the bacterial communities of bamboo shoots (Dendrocalamus latiflorus) during pickling process

Impact of whole grain highland hull-less barley on the denaturing gradient gel electrophoresis profiles of gut microbial communities in rats fed high-fat diets

Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) is a traditional non-culture technique that can provide a fingerprint of the microbial community. In the field of gut microbiota analysis, PCR-DGGE still holds potential for development. In the present study, we utilized an improved nested PCR-DGGE approach targeting the V3 region of 16S ribosomal DNA to investigate the impact of whole grain highland hull-less barley (WHLB), a cereal known for its significant hypocholesterolemic effect, on the gut microbiota profiles of high-fat diet rats. Seventy-two male Sprague-Dawley rats were divided into four groups and fed a normal control diet, a high-fat diet, or a high-fat diet supplemented with a low or high dose of WHLB for 4 or 8 weeks. The results revealed that the dominant bands varied among different dose groups and further changed with different treatment times. The compositions of bacterial communities in feces and cecal content were similar, but the dominant bacterial bands differed. After performing double DGGE, extracting the bands, sequencing the DNA, and aligning the sequences, a total of 19 bands were classified under the Firmicutes and Bacteroidetes phyla, while two bands were identified as unclassified uncultured bacteria. The relative abundance of Lactobacillus gasseri, Uncultured Prevotella sp., and Clostridium sp. increased following the administration of WHLB. Illumina-based sequencing was employed to assess the reliability of DGGE, demonstrating its reliability in analyzing the dominant taxonomic composition, although it may have limitations in accurately detecting the alpha diversity of bacterial species.

IMPORTANCE

While next-generation sequencing has overshadowed polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), the latter still holds promise for advancing gut microbiota analysis due to its unique advantages. In this study, we used optimized nested PCR-DGGE to investigate the gut microbiota profile of high-fat diet rats after administering whole grain highland hull-less barley. High-throughput sequencing was employed to validate the DGGE results. Our results proved the reliability of PCR-DGGE for analyzing the dominant taxonomic composition while also providing visual evidence of a notable relationship between the composition of cecal and fecal microbial communities, highlighting substantial differences in both richness and abundance.

A Study on the Formation of Flavor Substances by Bacterial Diversity in the Fermentation Process of Canned Bamboo Shoots in Clear Water

Canned bamboo shoots in clear water could produce a unique flavor through bacterial diversity via the fermentation process. Weissella, Streptococcus, Leuconostoc, Acinetobacter, Lactococcus and Lactobacillus were the main microorganisms. Tyrosine was the most abundant free amino acid (FAA), which had a negative correlation with Lactococcus. Ten kinds of flavor substances, such as 3-methyl-1-butanol, acetic acid, 2-phenylethyl ester, benzene acetaldehyde, benzoic acid and ethyl ester, were important influential factors in the flavor of fermented bamboo shoots. Through the verification test of tyrosine and phenylalanine decarboxylase, it was found that Lactococcus lactis TJJ2 could decompose tyrosine and phenylalanine to produce benzaldehyde and benzene acetaldehyde, which provided the fermented bamboo shoots with a grassy aroma.

Dynamic Changes in Flavor and Microbiota in Traditionally Fermented Bamboo Shoots (Chimonobambusa szechuanensis (Rendle) Keng f.)

Dissecting flavor formation and microbial succession during traditional fermentation help to promote standardized and large-scale production in the sour shoot industry. The principal objective of the present research is to elucidate the interplay between the physicochemical attributes, flavor, and microbial compositions of sour bamboo shoots in the process of fermentation. The findings obtained from the principal component analysis (PCA) indicated notable fluctuations in both the physicochemical parameters and flavor components throughout the 28 day fermentation process. At least 13 volatile compounds (OAV > 1) have been detected as characteristic aroma compounds in sour bamboo shoots. Among these, 2,4-dimethyl Benzaldehyde exhibits the highest OAV (129.73~668.84) and is likely the primary contributor to the sour odor of the bamboo shoots. The analysis of the microbial community in sour bamboo shoots revealed that the most abundant phyla were Firmicutes and Proteobacteria, while the most prevalent genera were Enterococcus, Lactococcus, and Serratia. The results of the correlation analysis revealed that Firmicutes exhibited a positive correlation with various chemical compounds, including 3,6-nonylidene-1-ol, 2,4-dimethyl benzaldehyde, silanediol, dimethyl-, nonanal, and 2,2,4-trimethyl-1,3-pentylenediol diisobutyrate. Similarly, Lactococcus was found to be positively correlated with several chemical compounds, such as dimethyl-silanediol, 1-heptanol, 3,6-nonylidene-1-ol, nonanal, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, dibutyl phthalate, and TA. This study provides a theoretical basis for the standardization of traditional natural fermented sour bamboo production technology, which will help to further improve the flavor and quality of sour bamboo.

Isolation of Efficient Xylooligosaccharides-Fermenting Probiotic Lactic Acid Bacteria from Ethnic Pickled Bamboo Shoot Products

Xylooligosaccharides (XOSs) are produced from xylan, which is a component of the hemicellulose that can be found in bamboo shoots. Naw Mai Dong, an ethnic pickled bamboo shoot product of northern Thailand, is generally characterized as acidic and has a sour taste. It can be considered a potential source of probiotic lactic acid bacteria (LAB). This study aimed to isolate efficient XOSs-fermenting probiotic LAB from ethnic pickled bamboo shoot products. A total of 51 XOSs-fermenting LAB were recovered from 24 samples of Naw Mai Dong, while 17 strains exhibited luxuriant growth in xylose and XOSs. Among these, seven strains belonging to Levicaseibacillus brevis and Pediococcus acidilactici exhibited similar growth in glucose, xylose, and XOSs, while the rest showed a weaker degree of growth in xylose and XOSs than glucose. Sixteen strains exhibited resistance under gastrointestinal tract conditions and displayed antimicrobial activity against foodborne pathogens. Notably, Lv. brevis FS2.1 possessed the greatest probiotic properties, with the highest %hydrophobicity index and %auto-aggregation. Effective degradation and utilization of XOSs by probiotic strains are dependent upon xylanase and β-xylosidase production, as well as xylose metabolism. It can be concluded that pickled bamboo shoot products can be a beneficial source of XOSs-fermenting probiotic LAB.

Evaluation and comparison of the microbial communities and volatile profiles in homemade suansun from Guangdong and Yunnan provinces in China

BACKGROUND

Suansun is a traditional salt-free fermented bamboo shoot product that has been widely consumed as a cooking ingredient in south China for centuries. The aim of this study was to evaluate and compare the microbial and metabolic diversity in samples of two kinds of suansun, namely Guangdong suansun (GD) and Yunnan suansun (YN), using high-throughput sequencing (HTS) and headspace solid-phase microextraction-gas chromatograph-mass spectrometry (HS-SPME/GC-MS), respectively, and then to assess the influence of environmental factors on the microbial communities.

RESULTS

The results showed that Lactobacillus and Serratia were the most abundant bacterial genera in both the GD and YN groups. For the fungi, Pichia, Candida, and Debaryomyces were the major genera in the GD group, whereas Pichia and Zygosaccharomyces were the dominant genera in the YN group. The canonical correlation analysis (CCA) results demonstrated that three environmental factors - temperature, longitude, and altitude - play a more important role in affecting the microbial community composition of suansun than physical and chemical factors. The fugal community composition was more influenced by environmental factors than the bacterial community. The volatile profile of the GD group differed from that of the YN group, and the difference was mainly reflected in the relative alcohol, aldehyde, ester, and aromatic compound content.

CONCLUSIONS

This study provided insights into the microbial and metabolic profiles of suansun products. The findings might be useful for the improvement and standardization of suansun production. © 2020 Society of Chemical Industry.

Hypocholesterolaemic effect of whole-grain highland hull-less barley in rats fed a high-fat diet

Whole-grain highland hull-less barley (WHLB) contains high amounts of bioactive compounds that potentially exhibit cholesterol-lowering effects. This study investigated the hypocholesterolaemic effect of WHLB. A total of seventy-two male Sprague–Dawley rats were divided into four groups and were fed with the normal control diet, high-fat diet (HFD) and HFD containing low or high dose (10 or 48·95 %) of WHLB. High dose of WHLB significantly decreased the organ indexes of liver and abdominal fat and lipid levels of plasma and liver in HFD rats. The lipid regulation effect of WHLB, which was reconfirmed through hepatocyte morphologic observation, was accompanied by a large excretion of bile acids in the small intestinal contents and the faeces. Real-time PCR analyses, which were further reconfirmed through Western blot analyses, revealed that a high dose of WHLB significantly enhanced the hepatic expressions of AMP-activated protein kinase α, cholesterol 7α-hydroxylase, LDL receptor, liver X receptor, and PPARα and decreased the expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase. It also enhanced the ileal expression of farnesoid X receptor and resulted in the decrease of expression of apical sodium-dependent bile acid transporter. WHLB exhibited hypocholesterolaemic effects mainly by inhibiting cholesterol synthesis, cholesterol accumulation in peripheral tissue, and bile acid reabsorption and by stimulating bile acid synthesis.