Guozhong Zhao

Comparison and analysis of fatty acids, sterols, and tocopherols in eight vegetable oils.

The similarities and differences of eight vegetable oils produced in China were investigated in terms of their fatty acid, sterol, and tocopherol compositions and subsequent data processing by hierarchical clustering analysis and principal component analysis. The lipid profiles, acquired by analytical techniques tailored to each lipid class, revealed great similarities among the fatty acid profiles of corn and sesame oil as well as few differences in their sterol profiles. It turns out that not only was there great similarity between the fatty acid profiles of corn oil and sesame oil but also there were not too many differences for the sterol profiles. Sunflower and tea-seed oil showed similar sterol compositions, while the tea-seed oil tocopherol was very similar to palm oil. The results demonstrated that the use of only one of these profiles was unreliable for indentifying oil origin and authenticity. In contrast, the use of the sterol or tocopherol profile together with the fatty acid profile more accurately discriminates these oils.

Microstructural and lipid composition changes in milk fat globules during milk powder manufacture

The purpose of this study was to investigate the effects of milk powder processing conditions (pasteurisation, homogenisation and spray-drying) on the microstructure and composition of fat globules in cow milk. In general, the process of pasteurisation results in fewer changes in the microstructure and lipid composition than do other processing methods. The phospholipid, sterol, and the fatty acid composition of the phospholipids, with the exception of the fatty acids of total lipids, underwent significant changes under different processing conditions compared with the untreated milk fat globules. The contents and distribution of the phospholipids in pasteurised milk indicated a high level of stability, but the amounts of phosphatidylethanolamine, phosphatidylserine, and sphingomyelin were significantly affected by homogenisation. A reduction in the cholesterol content was observed after pasteurisation and homogenisation. The results indicate that processing had a significant effect on the composition and structure of the membrane of the phospholipids in milk fat globules.

Metabolism of Fructooligosaccharides in Lactobacillus plantarum ST-III via Differential Gene Transcription and Alteration of Cell Membrane Fluidity.

ABSTRACT Although fructooligosaccharides (FOS) can selectively stimulate the growth and activity of probiotics and beneficially modulate the balance of intestinal microbiota, knowledge of the molecular mechanism for FOS metabolism by probiotics is still limited. Here a combined transcriptomic and physiological approach was used to survey the global alterations that occurred during the logarithmic growth of Lactobacillus plantarum ST-III using FOS or glucose as the sole carbon source. A total of 363 genes were differentially transcribed; in particular, two gene clusters were induced by FOS. Gene inactivation revealed that both of the clusters participated in the metabolism of FOS, which were transported across the membrane by two phosphotransferase systems (PTSs) and were subsequently hydrolyzed by a β-fructofuranosidase (SacA) in the cytoplasm. Combining the measurements of the transcriptome- and membrane-related features, we discovered that the genes involved in the biosynthesis of fatty acids (FAs) were repressed in cells grown on FOS; as a result, the FA profiles were altered by shortening of the carbon chains, after which membrane fluidity increased in response to FOS transport and utilization. Furthermore, incremental production of acetate was observed in both the transcriptomic and the metabolic experiments. Our results provided new insights into gene transcription, the production of metabolites, and membrane alterations that could explain FOS metabolism in L. plantarum.

Gene regulation in Aspergillus oryzae promotes hyphal growth and flavor formation in soy sauce koji

Aspergillus oryzae 100-8 and the parental strain A. oryzae 3.042 are used in soy sauce fermentation in China. The growth rate of A. oryzae 100-8 is faster than A. oryzae 3.042, and the soy sauce flavors obtained with A. oryzae 100-8 fermentation are better than those obtained with A. oryzae 3.042. In this study, comparisons were made through biomass, reactive oxygen species (ROS) and gas chromatography-mass spectrometry (GC-MS) measurements, and the reasons for these differences were investigated through transcriptome and qRT-PCR analysis. The analysis indicated that several unique genes are closely associated with hyphal growth and flavor formation, as demonstrated by changes in the expression levels of these genes. These unique genes regulate hyphal growth and flavor formation in soy sauce koji fermentation.

Role of lactic acid bacteria on the yogurt flavour: A review

ABSTRACT Considerable knowledge has been accumulated on the lactic acid bacteria (LAB) that affect the aroma and flavour of yogurt. This review focuses on the role of LAB in the production of flavour compounds during yogurt fermentation. The biochemical processes of flavour compound formation by LAB including glycolysis, proteolysis, and lipolysis are summarised, with some key compounds described in detail. The flavour-related activities of LAB mostly depend on the species used for yogurt fermentation, and some strategies have been developed to obtain more control of the flavour-forming process. Metabolic engineering can be a powerful tool to reroute the metabolic flux towards the efficient accumulation of the desired flavour compounds with the knowledge of the complex network of flavour-forming pathways and the availability of genetic tools. Further progress made in the omics-based techniques and the use of systems biology approaches are needed to fully understand, control, and steer flavour formation in yogurt fermentation processes.

Effects of freeze drying and spray drying on the microstructure and composition of milk fat globules

Freeze drying and spray drying are conventional methods for converting milk into powder in the dairy industry. The purpose of this study was to investigate the effects of these drying methods on the physical, chemical and structural features of milk fat globules (MFGs). The globule sizes increased after freeze drying and spray drying, but the integrity of their microstructures was still maintained. Compared with that in untreated MFGs, the composition of the fatty acids underwent fewer changes under the two different drying conditions. The main phospholipids showed some differences between the freeze-dried milk and spray-dried milk, and the saturation of the fatty acids of phospholipids was increased after the drying treatments. A reduction in the cholesterol content was observed after the freeze-drying and spray-drying processes. The level of unsaturation decreased as the diameter of the globules increased. The results indicated that freeze drying had a significant effect on the liquid-ordered domains in the MFG membrane, which was formed by sphingolipids and cholesterol. However, spray drying influenced the liquid-disordered domains, which were formed by glycerophospholipids. Thus, the drying method appears to affect the physical, chemical and microstructure characteristics of MFGs, which may affect the stability of the globules in milk and the way the milk is digested.

Production of exopolysaccharide by Bifidobacterium longum isolated from elderly and infant feces and analysis of priming glycosyltransferase genes

The exopolysaccharide (EPS) production of several Bifidobacterium longum strains isolated from infant and elder feces was determined. The relationship between EPS production and tolerance to artificial gastric and intestinal juices was analyzed. Moreover, priming glycosyltransferase (pGT) gene fragments of these strains were amplified and sequenced. The results indicate that their tolerance correlated well with EPS production, especially the production of cell-surface-bound exopolysaccharide (EPS-b). The EPS-b production by strains isolated from elderly volunteers was found to be significantly higher than that produced by strains isolated from infants. Lastly, the phylogenetic tree of the pGT gene sequence fragments showed that the pGT genes of infant-originated B. longum strains had greater homology than those of elder-originated strains.

Specificity of acyl-CoA binding protein to acyl-CoAs: influence on the lipid metabolism in Aspergillus oryzae

Acyl-CoA binding protein (ACBP) is involved in lipid metabolism and regulation of gene expression in eukaryotic cells, however, the specific functional roles of this important class of proteins remain to be elucidated. We have cloned and expressed a recombinant Aspergillus oryzae ACBP (AoACBP) that has a preference for binding relatively long chain acyl-CoAs such as palmitoyl (C16:0)-CoA (Kd = 82 nM) and stearoyl (C18:0)-CoA (Kd = 59 nM) by microscale thermophoresis binding assay. The high affinities for binding C16:0-CoA and C18:0-CoA were also conformed to the composition of fatty acids in A. oryzae 3.042. Moreover, the increased AoACBP levels were analyzed by Western blot procedure. And the expression levels and distribution patterns of AoACBP in this fungal life cycle were also investigated by RT-PCR and immunofluorescence. The accumulation of AoACBP have an effect on lipid metabolism, and it was significantly increased from 24 to 48 h suggest that AoACBP plays an important role in the later growth stage of A. oryzae 3.042 for fatty acid synthesis.