Food Bioengineering最新文献

Chitooligosaccharides (COSs) and d-glucosamine (GlcN), the most valuable biomolecules due to their various physiological functions, can be available inexpensively from chitosan by bio-enzymatic degradation, in which chitosanases play a key role. On the other hand, pretreatment of chitosan is the necessary procedure in the bioproduction by enzymatic hydrolysis. Therefore, the green and efficient pretreatment strategy as well as superior enzyme activity are the most critical aspects in scaled up production. This study investigated environmentally friendly and efficient enzymatic hydrolysis of powdery chitosan (PC) pretreated by ball-milling. First, heterologous expression yielded OUC-CsnPT, a glycoside hydrolase family 46 chitosanase with a predominant specific activity of 5346.56 U/mg at pH 6.0°C and 45°C. The endo-type chitosanase OUC-CsnPT hydrolyzed chitosan to produce GlcN and chitobiose [(GlcN)₂]. Then, ball-milling was employed to pretreat PC to promote chitosanase OUC-CsnPT hydrolysis, and the effectiveness was characterized by scanning electron microscope, X-ray diffraction, and FTIR-attenuated total reflection. Through the development of the novel route, the yield of COSs and GlcN for ball-milling powdery chitosan increased by 10.8-folds with a concentration of 14.5 μmol/ml. Hence, this technique presents a promising strategy suited to be a straightforward and environmentally friendly option for oligosaccharides production, broadening the theoretical basis for PC biodegradation.

Physicochemical properties of three types of barley flour, whole barley flour (BF), electromagnetic stir-frying whole barley flour, and extruded whole barley powder (EBF), and their potential application in emulsion type sausage were evaluated in this study. The water solubility index, water absorption index, and pasting properties of barley flour treated by different processing technologies were significantly different. The EBF has the highest water solubility index (12.67%) and water absorption index (503.20%), and with the minimum peak viscosity (2593.67 cp) and pasting temperature (50.20°C). The water-holding capacity and cooking loss of emulsified sausage improved significantly after adding the barley flour processed by different methods, especially the 9%BF substitution, the pressure water loss rate and cooking loss rate were reduced to 5.32% and 14.52%, respectively. The emulsified sausage added with BF indicated better color quality and texture properties comparable with the control. Scanning electron microscopy also showed that the addition of three kinds of barley flour in sausage formation led to a difference in the microstructure of the sausages. This study suggested that barley flour improved the physicochemical and textural properties of the emulsified sausage.

Obesity and its related complications have become increasingly serious social problems that threaten people's lives. Lactic acid bacteria (LAB) have shown an effective influence on preventing obesity in animal experiments and human clinical trials, but its exact mechanism remains unclear. In this review, LAB and several of its metabolites are taken as the point of penetration. It is aimed to summarize the relationship between obesity and gut microbiota, the efficacy of LAB, and its potential mechanisms of preventing obesity and lipid metabolism. LAB intervention can regulate gut microbiota and improve intestinal permeability which is damaged by a high-fat diet or lipopolysaccharide. Besides  this, some metabolites produced by LAB can be involved in regulating host lipid metabolism-related pathways. Short-chain fatty acids, linoleic acid, and gamma-aminobutyric acid, taken as representatives here, can participate in the regulation through AMP-activated protein kinase or peroxisome proliferator-activated receptor pathway and bowel–brain axis. Therefore, the ingestion of LAB may become a potential adjunctive treatment for obesity in future.

Lactoferrin is an 80 kDa iron-binding glycoprotein of the transferrin family, which is abundant in milk and in most biological fluids. Besides the direct antimicrobial properties, lactoferrin can regulate immune responses and prevent infection and septic shock. Membrane adsorption and chromatographic methods are usually used for separating and purifying of lactoferrin from bovine milk. However, the content of lactoferrin in milk is relatively low, resulting in a high cost of producing lactoferrin. Meanwhile, as a heterologous protein applied to the human body, it may cause a certain antigen response. Therefore, obtaining a large amount of biologically active lactoferrin has always been a research hot topic. This review first introduced the physical and chemical properties, and biological activities of lactoferrin. Then, the current recombinant expression systems for lactoferrin were summarized. Finally, the current challenges and the future development trends of efficient synthesis of lactoferrin were discussed.

Whole wheat flour (WWF) is regarded to have preventive effects on life-style diseases. Detection, identification and isolation of WWF-responsive gut indigenous bacteria (RIB) should reveal the gut microbiota-mediated properties of WWF. To confirm the existence and roles of bread flour (BF)- and WWF-RIB, Institute of Cancer Research mice were fed a diet containing corn starch (CS), BF or WWF as the starch source for 14 days. WWF increased in defecation. BF- and WWF-RIB were detected using 16S rRNA(V4) gene amplicon sequencing. Amplicon sequence variants (ASVs) of Lactobacillus johnsonii-like bacteria in both BF and WWF groups (respective relative abundance: 9.3% and 9.4%) were higher than those in the CS group (0.5%). While Lactobacillus intestinalis- and Limosilactobacillus reuteri-like bacteria ASVs were high in the WWF group (0.8% and 1.7%, respectively), these were not detected in the CS group. In contrast, ASVs of Blautia-, Clostridium saudiense/disporicum-, Lactobacillus murinus-, Muribaculaceae-, Phocaeicola vulgatus- and Bifidobacterium pseudolongum-like bacteria in CS-fed mice were higher than those in the other mice. Among these BF- and WWF-RIB, L. johnsonii and L. reuteri could be isolated. Further studies on the isolation of the RIB from the human gut are required.

As a rare low-calorie sugar with special medicinal value, d-tagatose is widely used in the field of food, beverages, medicine, and cosmetics. However, enzymatic d-tagatose production in vitro is commonly limited to low conversion efficiency and poor thermo-stability. Herein, taking advantage of the self-assembling property of protein scaffold EutM (ethanolamine bacterial microcompartments), Spy and Snoop peptide pairs was used to drive the linkage between the EutM and cargo proteins, β-galactosidase (BagB), and l-arabinose isomerase (TMAI) to construct a dual-enzymes cascade and realize the d-tagatose production from lactose. The optimal conditions of the cascade were shown to be pH of 8.0, temperature of 60°C, 100 g/L lactose as substrate with supplementing 5 mM Mn²⁺. When the ratio of immobilized enzymes to EutM scaffold reached 1:6, the d-tagatose productivity of the dual-enzymes cascade could reach 1.03 g/L/h, which was 1.24-fold higher than free enzymes. In addition, the EutM-based scaffold could efficiently improve the stability of immobilized enzymes, in which 45% of the activity remained after 12 h, 2.14-fold higher than the free one. Overall, an attractive EutM-based self-assembling platform immobilizing BagB and TMAI was developed, showing enhanced catalysis efficiency and enzyme thermo-stability for d-tagatose production.