Mannan oligosaccharides alleviate oxidative injury in the head kidney and spleen in grass carp(Ctenopharyngodon idella)via the Nrf2 signaling pathway after Aeromonas hydrophila infection

Background Mannan oligosaccharides(MOS)are recommended as aquaculture additives owing to their excellent antioxidant properties.In the present study,we examined the effects of dietary MOS on the head kidney and spleen of grass carp(Ctenopharyngodon idella)with Aeromonas hydrophila infection.Methods A total of 540 grass carp were used for the study.They were administered six gradient dosages of the MOS diet(0,200,400,600,800,and 1,000 mg/kg)for 60 d.Subsequently,we performed a 14-day Aeromonas hydrophila challenge experiment.The antioxidant capacity of the head kidney and spleen were examined using spectrophotometry,DNA fragmentation,qRT-PCR,and Western blotting.Results After infection with Aeromonas hydrophila,400-600 mg/kg MOS supplementation decreased the levels of reactive oxygen species,protein carbonyl,and malonaldehyde and increased the levels of anti-superoxide anion,antihydroxyl radical,and glutathione in the head kidney and spleen of grass carp.The activities of copper-zinc superoxide dismutase,manganese superoxide dismutase,catalase,glutathione S-transferase,glutathione reductase,and glutathione peroxidase were also enhanced by supplementation with 400-600 mg/kg MOS.Furthermore,the expression of most antioxidant enzymes and their corresponding genes increased significantly with supplementation of 200-800 mg/kg MOS.mRNA and protein levels of nuclear factor erythroid 2-related factor 2 also increased following supplementation with 400-600 mg/kg MOS.In addition,supplementation with 400-600 mg/kg MOS reduced excessive apoptosis by inhibiting the death receptor pathway and mitochondrial pathway processes.Conclusions Based on the quadratic regression analysis of the above biomarkers(reactive oxygen species,malondialdehyde,and protein carbonyl)of oxidative damage in the head kidney and spleen of on-growing grass carp,the recommended MOS supplementation is 575.21,557.58,531.86,597.35,570.16,and 553.80 mg/kg,respectively.Collectively,MOS supplementation could alleviate oxidative injury in the head kidney and spleen of grass carp infected with Aeromonas hydrophila.

Partial overlap of anti-mycobacterial,and anti-Saccharomyces cerevisiae mannan antibodies in Crohn's disease

AIM： To test whether humoral immune reaction against mycobacteria may play a role in anti- Saccharomyces cerevisiae antibodies （ASCA） generation in Crohn＇s disease （CD） and/or whether it correlates with clinical subtypes. METHODS： The dominant ASCA epitope was detected by Galanthus nivalis lectin （GNL）-binding assay. ASCA and IgG against mycobacterial lysates （M avium, M smegmatis, M chelonae, M bovis BCG M avium ssp. paratuberculosis （MAP）] or purified lipoarabinomannans （LAM） were detected by ELISA. ASCA and anti-mycobacterial antibodies were affinity purified to assess cross-reactivities. Anti-mycobacterial IgG were induced by BCG-infection of mice. RESULTS： GNL bound to different extents to mycobacterial lysates, abundantly to purified mannosecapped （Man） LAM from M tuberculosis, but not to uncapped LAM from M srnegrnatis. Fifteen to 45% of CD patients but only 0%-6% of controls were seropositive against different mycobacterial antigens. Anti-mycobacterial IgG correlated with ASCA （r = 0.37-0.64; P = 0.003-P 〈 0.001）. ASCA-positivity and deficiency for mannan-binding lectin synergistically associated with anti-mycobacterial IgG. In some patients, anti-mycobacterial antibodies represent crossreactive ASCA. Vice-versa, the predominant fraction of ASCA did not cross-react with mycobacteria. Finally, fistulizing disease associated with antibodies against M avium, M smegmatis and MAP （P = 0.024, 0.004 and 0.045, respectively）. CONCLUSION： Similar to ASCA, seroreactivity against mycobacteria may define CD patients with complicated disease and a predisposition for immune responses against ubiquitous antigens. While in some patients anti-mycobacterial antibodies strongly cross-react with yeast mannan; these cross-reactive antibodies only represent a minor fraction of total ASCA. Thus, mycobacterial infection unlikely plays a role in ASCA induction.

Characterization of β-1,4-D-mannanase Produced by Bacillus subtilis MSJ-5

Properties of enzyme production of a Bacillus subtitles strain （ MSJ-5 ） isolated from soil were studied in the test. Enzyme production reached the peak when MSJ-5 being cultured in fermentation medium for 32 h. 6-1,4-D-mannanase was the main component of crude enzyme solution, test results showed that the optimal reaction temperature of the enzyme was 50 ℃, the optimum reaction pH was 7.0, and the enzyme was stable when pH was 5.0 -7.0. Hydrolysis test re- suits showed that β-1,4-D-mannanase produced by MSJ-5 had significant viscosity reduction effects on Konjak mannan, and the major hydrolysis product was man- nan oligosaecharide. The results indicated that 6-1,4-D-mannanase produced by B. subtilis MSJ-5 had application potential in feed ingredients and functional oligo- saccharides industry.

Gut Bacterial and Lactobacilli Communities of Weaning Piglets in Response to Mannan Oligosaccharide and Sugar Beet Pulp In vitro Fermentation

Microbiota in the gastrointestinal tract （GIT） of piglets during weaning transition can experience a sharp change which could result in growth reduction and diarrhea of weaned piglets. Dietary manipulations can play an important role in attenuating such changes caused by weaning stress. Therefore, ileal and colonic contents of weaned piglets were used as inocula, mannan oligosaccharide （MOS） or sugar beet pulp （SBP） was supplied as single energy sources to investigate effects of MOS or SBP on the shifts of gastro-intestinal microflora and lactobacilli populations. The universal bacteria- and lactobacilli-specific PCR/denaturing gradient gel electrophoresis （DGGE）, cloning and sequencing techniques were used. DGGE profiles of the universal bacteria showed that great changes were found in the position, numbers and intensity of dominant bands after fermentation. The similarity of bacterial community between ileum and colon was increased to 85-97% by MOS or SBP treatment after fermentation from the similarity with 20% before fermentation. MOS treatment significantly increased the bacterial diversity and band number in both ileal and colonic fermentation （P〈0.05）. SBP treatment significantly increased the bacterial diversity and band number in colon （P〈0.05）. It implies that some species were enriched by the addition of MOS or SBP to increase the similarity and diversity of bacterial community in weaned piglets. Five specific bands appearing in MOS or SBP treatment group after fermentation were cloned and sequenced, the changes of species related to Prevotella and Ruminococcus were observed. Two bands related to uncultured bacterium with 98% similarity were detected by MOS or SBP treatment. However, there were no effects on the similarity, diversity index and lactobacilli species revealed by MOS or SBP treatment. These results imply that MOS or SBP could have beneficial effects on the weaning piglets by stablizing microbiota in the GIT microflora.

Effect of Konjac Mannan Oligosaccharides on Growth and Antibacterial Ability of Pseudosciaena crocea

[Objective]This experiment was conducted on Pseudosciaena crocea to study the effects of mannan oligosaccharides on growth and antibacterial ability. [Method]1 500 experimental fishes were divided into five groups. The control group（ C） contained no mannan oligosaccharides,the treatment groups were contained 100,200,400,800 mg /kg of konjac mannan oligosaccharides in basal diet,respectively. The experiment continued 4 months. [Result]The results showed that Konjac Mannan oligosaccharides could significantly improve weight gain Pseudosciaena crocea. Compared with control group,Test 2 group intestine protease activity increased by 45. 74%,hepatopancreatic lipase activity increased by 31. 37%,amylase activity increased by 27. 16%. Comparison with the control group,the test group serum SOD activity was significantly higher than that in the control group（ P 〈0. 05）. Lysozyme（ LZM） activity,spleen and serum test group was significantly higher than that in the control group（ P 〈0.05）. Pseudosciaena crocea were infected by Anguillarum,compared with control group,the survival rate is higher than that of the control group（ P 〈0. 05） when the dosage of 200 mg /kg,400 mg /kg. [Conclusion]According to the test results,the Konjac Mannan oligosaccharides in the basal diet suitable dosage were 200 mg /kg.

Isolation of Mannooligosaccharides Corresponding to Antigenic Determinants of Pathogenic Yeast <i>Candida catenulata</i>Cell Wall Mannan

To investigate the chemical structure of cell wall mannan of pathogenic yeast, Candida catenulata IFO 0745 strain, which possess the epitopes of antigenic factors 1, 9, and 34 to genus Candida, we previously performed the two-dimensional nuclear magnetic resonance (NMR) analysis of this mannan, Fr. C, without the need for harsh procedures. In this study, three oligosaccharides, biose, triose, and tetraose, and mannose were isolated from Fr. C by acetolysis. The results of NMR analysis indicate that the chemical structures of these oligosaccharides were identified to Manα1-2Man, Manα1-2Manα1-2Man, and Manα1-3Manα1-2Manα1-2Man. The most of resultant mannose seems to be originated from the α-1,6-linked mannan backbone which is recognized by antiserum to factor 9. The inhibition assay of slide agglutination reaction between Fr. C and antigenic antibodies using three oligosaccharides indicate that the Manα1-2Manα1-2Man and Manα1-3Manα1-2Manα1-2Man possess domains corresponding to immunodominants of antigenic factors 1 and 34, respectively.

Determination of <i>α</i>-1,3-Linked Mannose Residue in the Cell Wall Mannan of <i>Candida tropicalis</i>NBRC 1400 Strain

To investigate the chemical structure of cell wall mannan obtained from pathogenic yeast, Candida tropicalis NBRC 1400 (former antigenic standard strain, IFO 1400). As a result of two-dimensional NMR analysis, it was shown that the mannan of this strain is composed of α-1,6-, α-1,3-, α-1,2- and β-1,2-linked mannose residues. In this research, the mannan was subjected to three degradation procedures, acid-treatment, α-mannosidase, and acetolysis under two conditions in order to determine the chemical structure of the antigenic oligomannosyl side chains in this molecule. The 1H-nuclear magnetic resonance spectra of resultant oligosaccharides, pentaose and hexaose, demonstrated the existence of the oligomannosyl side chains corresponding to Manα1-3Manα1-2Manα1-2Manα1-2Man and Manα1-3Manα1-2Manα1-2Manα1-2Manα1-2Man, respectively, which have previously also been found in Candida albicans serotype A strain mannans. These findings indicate that C. tropicalis and C. albicans serotype A have no significant difference in the chemical structure of these cell wall mannans. Therefore, it can be interpreted that it is extremely difficult to distinguish both species by targeting the antigenic group in these mannans.

Effects of Dietary Mannan Oligosaccharides and Calcium Formate on Performance and Egg Quality of Japanese Quail （Coturnixjaponica）

The aim of this experiment was to study the effects of dietary supplementation of mannan oligosaccharides （MOS）, extracted from yeast Saccharomyces cerevisiae and acidifier calcium formate （CF） on some performance parameters and egg quality characteristics of Japanese quail （Coturnixjaponica）. During the experimental period, which lasted 90 days, one hundred eighty three, 42-day-old quail, were distributed into 4 groups of 3 replications each and were placed in separate wire suspended cages. The birds of control group received a commercial feed, while the birds of the other 3 groups received the same feed, to which either 6 g CF kg^-1 or 1 g MOS kg^-1 or both 6 g CF kg^-1 plus 1 g MOS kg^-1 were added. The live weight, feed consumption, feed conversion ratio and mortality of birds were not significantly affected. The addition of MOS in the feed significantly （P 〈 0.05） increased palmitic acid percentage of egg yolk. Also, the addition of CF significantly （P 〈 0.05） decreased egg shape index and palmitic acid percentage of egg yolk. Furthermore, significant （P 〈 0.05） interaction between MOS and CF was observed on palmitic acid percentage, egg shape index and egg shell thickness. No significant effect was observed for egg： weight, specific weight, parts percentage （yolk, albumen, shell）, shell deformation, yolk diameter and yolk colour （L＊a＊b＊ colour space）.

模式抗原Mannan-TTC的制备及免疫原性分析

目的:制备高免疫原性的模式抗原Mannan-TTC,分析其免疫原性。方法:将甘露聚糖(Mannan)与破伤风毒素C片段(TTC)蛋白进行化学交联,SDS-PAGE分析交联产物。用混合淋巴细胞反应检测DC负载Mannan-TTC刺激同种异体T细胞增殖的能力;WST-1和ELISA检测TTC特异性CD4+T细胞的增殖和分泌IFN-γ的能力;小鼠免疫后,用ELISA检测TTC特异性抗体水平。结果:成功交联Mannan与TTC,获得模式抗原Mannan-TTC。该交联产物能通过活化树突状细胞(DC),不仅增强了对同种异体T细胞增殖的能力,而且显著增强TTC抗原特异性的CD4+T淋巴细胞增殖及分泌细胞因子IFN-γ。动物免疫实验则显示,该交联产物能刺激小鼠免疫细胞产生TTC抗原特异性的抗体,但与单纯TTC抗原刺激相比,无显著性差异。结论:所获Mannan-TTC抗原免疫原性好,能显著增强细胞免疫应答,为研究体内外抗原提呈、免疫应答提供了良好的模式抗原。

Lipopolysaccharide immune stimulation but not β-mannanase supplementation affects maintenance energy requirements in young weaned pigs

Background: Pathogen or diet-induced immune activation can partition energy and nutrients away from growth,but clear relationships between immune responses and the direction and magnitude of energy partitioning responses have yet to be elucidated. The objectives were to determine how β-mannanase supplementation and lipopolysaccharide(LPS) immune stimulation affect maintenance energy requirements(MEm) and to characterize immune parameters, digestibility, growth performance, and energy balance.Methods: In a randomized complete block design, 30 young weaned pigs were assigned to either the control treatment(CON; basal corn, soybean meal and soybean hul s diet), the enzyme treatment(ENZ; basal diet + 0.056% β-mannanase),or the immune system stimulation treatment(ISS; basal diet + 0.056% β-mannanase, chal enged with repeated increasing doses of Escherichia coli LPS). The experiment consisted of a 10-d adaptation period, 5-d digestibility and nitrogen balance measurement, 22 h of heat production(HP) measurements, and 12 h of fasting HP measurements in indirect calorimetry chambers. The immune chal enge consisted of 4 injections of either LPS(ISS) or sterile saline(CON and ENZ), one every48 h beginning on d 10. Blood was collected pre-and post-challenge for complete blood counts with differential,haptoglobin and mannan binding lectin, 12 cytokines, and glucose and insulin concentrations.Results: Beta-mannanase supplementation did not affect immune status, nutrient digestibility, growth performance,energy balance, or MEm. The ISS treatment induced fever, elevated proinflammatory cytokines and decreased leukocyte concentrations(P < 0.05). The ISS treatment did not impact nitrogen balance or nutrient digestibility(P > 0.10),but increased total HP(21%) and MEm(23%), resulting in decreased lipid deposition(-30%) and average daily gain(-18%)(P < 0.05).Conclusions: This experiment provides novel data on β-mannanase supplementation effects on immune parameters and energy balance in pigs and is the first to directly relate decreased ADG to increased MEm independent of changes in feed intake in immune challenged pigs. Immune stimulation increased energy partitioning to the immune system by 23% which limited lipid deposition and weight gain. Understanding energy and nutrient partitioning in immune-stressed pigs may provide insight into more effective feeding and management strategies.

Structural Investigation of Cell Wall Mannan Antigen Obtained from Pathogenic Yeast <i>Candida zeylanoides</i>

Antigenicity of pathogenic yeast Candida zeylanoides NBRC 10326 was found to have similar to that of Candida guilliermondii, but it was slightly different, i.e. NBRC 10326 strain cells react strongly with the factor antibodies 1, 4, and 9, and react relatively weakly with factor antibody 5. We have investigated the structural characteristic of cell wall mannan of this strain using a non-degradable method, nuclear magnetic resonance analysis. The results obtained from NMR analysis, the two-dimensional homonuclear Hartmann-Hahn, indicated that C. zeylanoides mannan contains α-1, 3-linked and β-1,2-linked oligomannosyl side chains corresponding to C. guilliermondii specific antigenic factor 9. In addition, it was found that the mannan contains β-1,2-linked oligomannosyl side chains attached to phosphate groups corresponding to anitigenic factor 5, which were not found in C. guilliermondii mannan.

Anomeric Proton and Carbon (H1-C1) NMR Chemical Shifts of Antigenic Mannans Obtained from Pathogenic Yeast <i>Candida tropicalis</i>

On two dimensional maps of 1H-13C correlation spectroscopy (H-C COSY) analysis for the mannan of Candida tropicalis, nine cross peaks of anomeric proton and carbon were useful for the purpose of obtaining information on the chemical structure of this molecule. Namely, the mannans was comb-like structure constructed with the linear α-1,6-linked polymannnosyl backbone and several oligomannnosyl side chains composed of α-1,2-, α-1,3-, and β-1,2-linkages. Therefore, in the structural investigation of comb-like mannan, two-dimensional H-C COSY analysis is as useful as two-dimensional nuclear Hartmann-Hahn (HOHAHA) analysis.

魔芋甘露低聚糖增强肠道屏障功能改善酒精性中枢神经损伤的实验研究

目的慢性酒精摄入导致的大脑过度神经炎症是中枢神经损伤的重要危险因素。本实验主要研究魔芋甘露低聚糖(Konjac mannan oligosaccharides,KMOS)保护酒精喂养小鼠中枢神经炎症的作用及其机制。方法C57BL/6J小鼠采用Gao-binge法制备慢性酒精喂养小鼠模型,同时使用不同剂量的KMOS灌胃干预,喂养6周。评估脑组织皮层和海马区域神经元损伤和小胶质细胞活化情况,观察结肠组织损伤情况和炎症反应,检测血清LPS浓度。体外使用LPS直接刺激Caco-2细胞制备肠黏膜损伤模型。结果慢性酒精的摄入可导致小鼠大脑神经元损伤,而不同剂量的KMOS均能有效降低酒精喂养小鼠脑组织中小胶质细胞的活化状态,降低NLRP3炎性小体活化导致的炎性因子表达,减轻神经元受损。对结肠组织的分析结果表明,KMOS的使用有效地降低了酒精喂养小鼠外周血中内毒素LPS的浓度,减轻酒精喂养小鼠结肠组织的病理损伤和炎性反应,增强肠道组织Occludin表达。体外实验也显示,KMOS能显著抑制酒精暴露下Caco-2细胞的炎性反应,显著提高Occludin表达水平。结论KMOS的使用可有效的抑制酒精摄入导致的肠道炎症,修复肠道屏障,减少肠道LPS进入脑组织,降低小胶质细胞活化导致的过度神经炎症反应,进而改善脑神经元损伤。KMOS具有预防酒精性神经损伤的潜力。

甘露寡糖上调PIgR增强肉鸡肠道免疫屏障

为了探究甘露寡糖对肉鸡肠道屏障的影响,试验选用1日龄健康白羽肉仔鸡540只,肉鸡饲养至29日龄,按体重相近,公母各半的原则随机分为3组:模型对照组、甘露寡糖保健组和乳酸环丙沙星保健组,每组6个重复,每个重复30只,试验期为10 d。肉鸡30日龄时,模型对照组、甘露寡糖保健组、乳酸环丙沙星保健组肉鸡采用胸肌注射8.37×10^(9) CFU/mL的大肠杆菌菌液0.2 mL进行攻毒,之后分别给予饮用水、0.05 g/L甘露寡糖溶液和60 mg/L乳酸环丙沙星自由饮用,分别连用10 d。试验结束后对肉鸡称重,采集血液测定血清生化指标,采取小肠各段测定器官指数,通过RT-qPCR检测肉鸡肠道屏障关键基因表达。结果表明,模型对照组、甘露寡糖保健组和乳酸环丙沙星保健各组间各器官重、器官指数均无显著差异(P>0.05)。与模型对照组和乳酸环丙沙星保健组相比,甘露寡糖保健组肉鸡血清γ-谷氨酰转肽酶(γ-GGT)含量显著升高(P<0.05)。与模型对照组相比,甘露寡糖保健组肉鸡十二指肠多聚免疫球蛋白受体(PIgR)表达量显著升高(P<0.05);与乳酸环丙沙星保健组相比,甘露寡糖保健组肉鸡空肠PIgR表达量有升高的趋势(P=0.077)。综上所述,在饮水中添加甘露寡糖增加了血清γ-GGT,上调肉鸡十二指肠、空肠免疫屏障PIgR表达,增强肉鸡肠道免疫屏障,维护肠道健康,从而提高机体免疫能力,并相比乳酸环丙沙星效果更为显著。

血清MBL、HRG、IL-23/IL-17炎症轴与动脉瘤性蛛网膜下腔出血患者介入栓塞术后脑血管痉挛和预后的关系

目的探讨血清甘露聚糖结合凝集素(MBL)、富组氨酸糖蛋白(HRG)、白细胞介素(IL)-23/IL-17炎症轴与动脉瘤性蛛网膜下腔出血(aSAH)患者介入栓塞术后脑血管痉挛(CVS)和预后的关系。方法选取2019年3月至2022年2月该院收治的195例行介入栓塞术治疗的aSAH患者,根据术后第4天数字减影血管造影检查是否发生CVS及严重程度分为无CVS组(126例)、轻度CVS组(18例)、中度CVS组(39例)和重度CVS组(12例)。比较4组术前及术后3 d血清MBL、HRG、IL-23、IL-17水平。随访6个月,根据患者预后的不同分为预后良好组(137例)和预后不良组(58例)。采用多因素Logistic回归模型分析aSAH患者预后不良的影响因素。采用受试者工作特征(ROC)曲线分析血清MBL、HRG、IL-23、IL-17水平及其联合应用模型对aSAH患者预后不良的预测价值。结果195例aSAH患者介入栓塞术后CVS发生率为35.38%。术后3 d,轻、中、重度CVS组血清MBL、IL-23、IL-17水平高于无CVS组,其中重度CVS组高于中度CVS组,中度CVS组高于轻度CVS组(P<0.05);轻、中、重度CVS组血清HRG水平低于无CVS组,其中重度CVS组低于中度CVS组,中度CVS组低于轻度CVS组(P<0.05)。术后3 d,4组血清MBL、IL-23、IL-17水平高于术前,血清HRG水平低于术前(P<0.05)。预后良好组动脉瘤直径≥6 mm、动脉瘤个数>1个、手术时间>24 h、Hunt-Hess分级Ⅲ/Ⅳ级、术后CVS患者例数占比及术后3 d血清MBL、IL-23、IL-17水平均低于预后不良组,术后3 d血清HRG水平高于预后不良组(P<0.05)。多因素Logistic回归分析显示,动脉瘤直径≥6 mm、Hunt-Hess分级Ⅲ/Ⅳ级、术后CVS、术后3 d MBL、IL-23、IL-17水平升高及HRG水平降低均是导致aSAH患者预后不良的独立危险因素(P<0.05)。ROC曲线结果显示,术后3 d血清MBL、HRG、IL-23、IL-17这4项指标对aSAH患者预后不良均有一定的预测效能。4项指标联合应用的预测模型效能较高(曲线下面积为0.853)。结论aSAH患者介入栓塞术后血清MBL、IL-23、IL-17水平升高及HRG水平下降可导致CVS发生风险增加,且与aSAH患者介入栓塞术后的预后不良有关。上述指标对aSAH患者预后不良有一定的预测效能。

甘露聚糖的理化特性、制备、测定和代谢途径及其应用的研究进展

甘露聚糖是一种天然的多糖物质,广泛分布于酵母菌、植物组织中。甘露聚糖作为饲料添加剂能够增强动物体液免疫和细胞免疫的能力,保持肠道微生态平衡并改善瘤胃功能。文章分别对甘露聚糖的理化特性、制备、测定和代谢途径及其应用进行了归纳和总结,以期为甘露聚糖的开发应用提供参考价值。

甘露寡糖调控体外瘤胃发酵和菌群结构的作用研究

本试验旨在研究甘露寡糖调控体外瘤胃发酵和菌群结构的作用。采用完全随机设计,共设置4个组,对照组(CON组)在发酵液中不添加甘露寡糖,试验组分别在发酵液中添加0.5%(低剂量组,LMO组)、1.0%(中剂量组,MMO组)和3.0%(高剂量组,HMO组)甘露寡糖,每组设置6个重复。试验以苜蓿干草为发酵底物,开展24 h体外瘤胃发酵试验,研究甘露寡糖对产气参数、发酵参数和菌群结构的调控作用。结果表明:1)与CON组相比,MMO组24 h累积产气量、理论最大产气量和总挥发性脂肪酸浓度均显著提高(P<0.05);HMO组24 h累积产气量、产气速率和总挥发性脂肪酸浓度均显著提高(P<0.05),氨态氮(NH3-N)浓度显著降低(P<0.05)。各组间乙酸和丙酸摩尔比以及乙酸/丙酸值均无显著差异(P>0.05)。2)与CON组相比,HMO组厚壁菌门(Firmicutes)和瘤胃球菌属(Ruminococcus)相对丰度显著提高(P<0.05),普雷沃氏菌属1(Prevotella_1)(P=0.065)和克里斯藤森菌科R-7群(Christensenellaceae_R-7_group)(P=0.075)相对丰度有提高趋势。3)体外瘤胃发酵参数与菌群相关性分析结果表明,厚壁菌门相对丰度与乙酸、丙酸和总挥发性脂肪酸浓度呈显著正相关(P<0.05);瘤胃球菌属相对丰度与24 h累积产气量、产气速率以及乙酸、丙酸和总挥发性脂肪酸浓度均呈显著正相关(P<0.05),与NH3-N浓度呈显著负相关(P<0.05)。综上所述,甘露寡糖对体外瘤胃发酵有积极影响,能够通过调控瘤胃菌群结构,提高瘤胃球菌属相对丰度和氮利用能力,增加总挥发性脂肪酸产量,但不改变发酵模式。

基于双菌偶联分阶段培养诱导酵母细胞壁释放甘露聚糖的研究

试验旨在实现酵母细胞壁甘露聚糖的高效释放及寡糖化。试验提出一种新型的双菌偶联分阶段培养模式,诱导酵母细胞壁释放甘露聚糖,通过筛选诱导菌株、双菌分阶段发酵验证释放多糖的效果。结果显示,试验通过对比测定4种芽孢杆菌对酿酒酵母细胞壁破壁率、甘露聚糖释放率的影响,确立了枯草芽孢杆菌-FMTK01-酿酒酵母双菌分阶段培养模式。双菌分阶段培养72 h时,酵母破壁率达到96.63%,甘露聚糖释放量达到83.87%。经过甘露聚糖解聚化分析可知,双菌分阶段培养模式实现了37.27%的酵母甘露聚糖的寡糖化。研究表明,试验提出的双菌偶联分阶段培养发酵模式可加速酵母细胞壁释放甘露聚糖以及多糖寡糖化,对其他生物多糖及其寡糖的制备具有一定的借鉴意义。

B.amyloliquefaciens T12高产β-甘露聚糖酶发酵优化及降解产物益生元活性研究

试验旨在提高枯草芽孢杆菌B. amyloliquefaciens T12甘露聚糖酶产酶量,验证水解产物的益生元活性。试验对发酵条件进行优化,单因素试验分别考察了8组培养变量对产酶活性影响,从影响β-甘露聚糖酶酶活力的单因素条件中筛选出3个主要因素,最陡爬坡试验确定主要因素中心点,最后采用Box-Behnken法设计并进行三因素三水平试验,通过Desgin Expert结果分析与后续试验验证。结果显示,最优发酵条件为魔芋粉浓度10.4g/L、酵母提取物6.37 g/L、装液量100 mL、接种量2%(体积分数)、发酵周期12~16 h、初始pH值6.5,其余条件不变。通过优化工艺发酵产酶,酶活力达到15 264.92 U/mL。对β-甘露聚糖酶水解产物甘露寡糖进行益生元活性分析,发现甘露寡糖对乳酸菌、干酪乳杆菌的生长均具有促进作用,且益生菌培养液具有抑制病原菌繁殖能力。