为什么植物多糖发酵后多糖含量增加了

Lytic polysaccharide monooxygenases (LPMOs) can oxidatively break the glycosidic bonds of crystalline cellulose, providing more actionable sites for cellulase to facilitate the conversion of cellulose to cello-oligosaccharides, cellobiose and glucose. In this work, a bioinformatics analysis of BaLPMO10 revealed that it is a hydrophobic, stable and secreted protein. By optimizing the fermentation conditions, the highest protein secretion level was found at a IPTG concentration of 0.5 mM and 20 h of fermentation at 37 °C, with a yield of 20 mg/L and purity > 95%. The effect of metal ions on the enzyme activity of BaLPMO10 was measured, and it was found that 10 mM Ca2+ and Na+ increased the enzyme activity by 47.8% and 98.0%, respectively. However, DTT, EDTA and five organic reagents inhibited the enzyme activity of BaLPMO10. Finally, BaLPMO10 was applied in biomass conversion. The degradation of corn stover pretreated with different steam explosions was performed. BaLPMO10 and cellulase had the best synergistic degradation effect on corn stover pretreated at 200 °C for 12 min, improving reducing sugars by 9.2% compared to cellulase alone. BaLPMO10 was found to be the most efficient for ethylenediamine-pretreated Caragana korshinskii by degrading three different biomasses, increasing the content of reducing sugars by 40.5% compared to cellulase alone following co-degradation with cellulase for 48 h. The results of scanning electron microscopy revealed that BaLPMO10 disrupted the structure of Caragana korshinskii, making its surface coarse and poriferous, which increased the accessibility of other enzymes and thus promoted the process of conversion. These findings provide guidance for improving the efficiency of enzymatic digestion of lignocellulosic biomass.

The analysis of the chemical composition of the vegetable raw materials received from leaves of an aspen ordinary, family plants Willow (Salicaceae), growing in the territory of the Khanty-Mansi autonomous district Yugra is provided in article. The choice of raw materials is caused by a large supply and fast reproducibility of a raw resource. In work numerical indicators and indicators of high quality of raw materials are established (humidity, the general ashes, sulphatic ashes, ashes not soluble in 10% to hydrochloric acid, extractive substances). The way of extraction of vegetable raw materials is reasonable, the comparative characteristic of content of extractive substances is provided in the received extracts. It is shown that the average content of extractive substances in native samples is 27.9%, the content of polysaccharides – 10.9%. The qualitative and quantitative analysis of biologically active agents is carried out by method of a highly effective liquid chromatography. The dominating components in samples of the plants growing in the territory of one land plot are салицин 510 mg of %, гиперозид 170 mg of %, routines of 210 mg of %. Influence of process of fermentation on the chemical composition of the vegetable raw materials received from leaves of an aspen ordinary is studied. The greatest exit of phenolic connections at impact on vegetable raw materials of fermentation is established by cold. The positive effect of impact of fermentation by crushing on quantity of the identified biologically active components is defined. Work was carried out for assessment of phytochemical parameters of quality of vegetable raw materials and formation of justification of analytical approaches to diagnostics of vegetable raw materials of the explored territory.

The consumption of plant-based foods have been increasing in the last years. Such rise is related to health and environmental benefits provided by these food products. In this sense, legumes represent an important constituent of plant-based diets due to its high nutritional content thereby making them a good option for replacing certain products of animal origin. Furthermore, one of the most interesting aspects of legumes are related to its low glycaemic properties that have been shown to be beneficial for health especially to sectors of the population with metabolic disorders. It has been found that microstructural aspects of legumes are responsible of such effects since in these systems, starch is naturally encapsulated within a cell wall matrix of non-starch polysaccharides. Therefore, it is essential to understand the mechanism by which those structures confer these low glycaemic properties. In this thesis, we have used red kidney beans as model systems to provide more insights about the role of plant-tissue structure in starch digestion and fermentation. The first three studies of this thesis were focused on understanding the effect of cotyledon cells intactness during gastrointestinal digestion while the latter two chapters on colonic fermentation. For the first study, in-vitro digestion of cotyledon cells with different levels of cell wall integrity were tested in order to understand starch hydrolysis when entrapped within this matrix. Results indicated that by decreasing cell intactness, the rate of starch digestion increased. Moreover, it was also found that the cytoplasmic matrix, constituted by starch embedded in a protein matrix, reduced further the accessibility of amylase affecting also the rate of starch digestion. Since proteins were also encapsulated within a cell wall matrix, it was interesting to explore how the digestibility of this macromolecule was affected by the physical entrapment. Therefore, in the second study it was observed that cell wall encapsulation limited protein denaturation induced by thermal treatment causing a reduction in digestibility. High amounts of an indigestible protein fraction were identified when proteins were cooked during cell wall confinement. Disrupting cell wall integrity after applying thermal treatments did not increase the extent of protein digestion indicating the resistance of this fraction. Furthermore, as opposed to what found for starch, protein digestion was found to be unaffected by the presence of starch granules in the cytoplasmic matrix. In an attempt to provide a mechanistic explanation about the digestibility of starch when confined within an intact cell matrix a mathematical model was developed for the third study. It was demonstrated that the process behind the digestibility of starch entrapped in bean cells consisted of a series of steps that started with the diffusion of α-amylase through the cell wall. It was found that the porosity and the interaction of amylase with cell wall constituents limited enzyme diffusion. As a result, lower amount of enzymes were available within the cell causing a reduction in starch digestion. The model was validated using in-vitro starch digestion data with very accurate results. This approach provided a useful tool to understand the effect of plant-tissue encapsulation in starch hydrolysis. The following chapters of this thesis were designed to understand the effect of food structure in colonic fermentation. The simulator of the human microbial ecosystem (SHIME®) was used to determine the fate of starch fermentation when entrapped within a cell wall matrix. Results indicate that during the first days of fermentation, encapsulation reduced the amount of starch fermentation compared to a sample where cell intactness was disrupted. However, after 12 days of fermentation, the amount of starch utilized by the microbiota was comparable to a sample devoided of cell wall entrapment. Furthermore, it was also observed that bean supplementation changed the composition of the microbiota present in the three colon regions where higher amounts of Bifidobacterium were identified independently of the structural properties of the sample. By the use of a batch fermentation model it was possible to study the efficiency of the microbiota present in each colonic region and assess the changes in fermentation due to microbiota adaptation to bean cells. For the former, by providing equal amounts of substrate to colonic microbiota it was possible to determine that bacteria present in the descending colon was the most efficient in fermenting carbohydrates. This indicated that the high amounts of protein fermentation observed in-vivo are probably due to carbohydrate depletion instead of a preference of  microbiota to utilize protein. As for the later, the effect of microbial adaptation  was studied by using inocula obtained from the SHIME® system before and after 12 days of exposure to intact bean cells. It was found that bacterial adaptation to substrate increased fermentation efficiency since higher amounts of gas were produced. However, it was observed that structural integrity of bean cells affected the rate of starch utilization independently of the type of microbiota utilized.