Research Progress in Biological Control of Soft Rot of Amorphophallus konjac

In this paper,the main control methods of soft rot of Amorphophallus konjac are reviewed,with a focus on the current research status of using plant growth promoting rhizobacteria for biological control of soft rot of A.konjac,and future research directions are looked forward to.

不同光照强度下花魔芋(Amorphophallus konjac)与谢君魔芋(Amorphophallus xiei)光合特性及光保护机制研究

为探讨不同耐光性植物光合特性及光保护机制,本研究以耐高光的喜阴植物花魔芋(Amorphophallus konjac K.Coch)和典型的喜阴植物谢君魔芋(Amorphophallus xiei H.Li&Z.L.Dao)为材料,测定与分析在透光率为100%、15%及2%光照条件下两种魔芋的光合能力、抗氧化酶活性及抗氧化物和光合色素组分的含量。结果表明,花魔芋最大光合速率和气孔导度随着生长环境光照强度降低而显著降低(P<0.05),谢君魔芋在透光率为15%时最大光合速率达最大值。大部分情况下,花魔芋的超氧化物歧化酶、抗坏血酸过氧化物酶、过氧化氢酶、谷胱甘肽还原酶活性比谢君魔芋高(P<0.05),而谢君魔芋具有较高的过氧化物酶活性(P<0.05)。总的来看,在中高光照环境下两种植物的抗氧化酶活性较高(P<0.05)。在透光率15%时,花魔芋谷胱甘肽和抗坏血酸显著比谢君魔芋高(P<0.05)。谢君魔芋的光合色素含量在透光率为15%时最高(P<0.05);相应地,花魔芋的光合色素含量在透光率为2%时含量最低(P<0.05);在不同光照强度下花魔芋光合色素含量基本上显著高于谢君魔芋(P<0.01)。本研究结果暗示,喜阴植物花魔芋耐受高光可能源于相对较高的光合作用能力和有效的光保护机制。

Screening of Antagonistic Actinomyces against Soft Rot of Amorphophallus konjac and Its Antibacterial Activity

[Objective] Antagonistic actinomyces of Amorphophallus konjac soft rot were isolated from the soil,the antibacterial activity of the fermentation was detected,and its active components were separated.[Method] The antagonistic actinomycetes were screened using plate confrontation culture method.The SJK18 antagonistic strain with strong activity was conducted single-factor tests using different carbon sources,nitrogen sources,temperatures and pH value as the culture condition,and the antibacterial activities of fermentation liquid was determined,respectively.The fermentation liquid of antagonistic strain was extracted with alcohol and acetic ester,and their antibacterial activities were determined.[Result] A total of 112 strains of actinomycetes were obtained,and 11 strains had antibacterial activity.The antibacterial activity of SJK18 strain was the strongest in the single-factor test,when the corn powder was adopted as the carbon sources,KNO3 was the nitrogen source,the temperature was 30 ℃ and the pH was 6.0,the appropriate pH value for the activity was 5.5-10.0.The diameters of inhibition zone of alcohol extract and raffinate of ethyl acetate were 17.0 and 20.0 mm,respectively,while the extraction of ethyl acetate had no antibacterial activity.[Conclusion] A strain of actinomyces with strong antibacterial activity against soft rot of A.konjac was obtained.

Effects of Intercropping on Rhizosphere Soil Bacterial Communities in Amorphophallus konjac

Soft rot disease causes heavy loss in konjac production every year, which caused by the genus Pectobacterium has been recognized as a major reason why konjac industry has not boomed in worldwide. However, intercropping with economically important trees can effectively control affect soft rot disease epidemics. Consequently, we conducted a rhizosphere bacterial diversity study to assess how intercropping affects soft rot disease using next-generation DNA sequencing. The results demonstrate the Shannon diversity index and Chao 1 index for soil bacteria were relatively steady under intercropping conditions, but changed greatly for the konjac monocrop with the increase in the number of cropping years. Of the 44 bacterial genera with relative abundance ratios of >0.3%, 11 were significantly affected by the duration of continuous cropping and the cultivation mode. Luteolibacter and Bacteroides showed highly significant differences between the monocrop and the intercrop for three continuous years. Pseudomonas was significantly affected by the different cultivation modes, while Myroides was significantly affected by planting age. Intercropping altered the structure and composition of the soil bacterial community, which led to a relative balance of beneficial bacteria, and the relative balance of beneficial bacteria is helpful to reduce the incidence of soft rot.

Constitutive and Secretory Expression of the AiiA in Pichia pastoris Inhibits Amorphophallus konjac Soft Rot Disease

Amorphophallus konjac is an important economic crop widely cultivated in Southeast Asia and Africa. However, A. konjac is seriously infected by soft rot pathogen. The endocellular acyl homoserine lactonase (AiiA) which is generated by Bacillus species has inhibitory effect on soft rot pathogen through disrupting the signal molecules (N-acylhomoserine lactones, AHL) of their Quorum Sensing system. The aim of our study is to obtain recombinant yeast which produces AiiA protein. The recombinant yeast Pichia pastoris GS115 was constructed to constitutive expression of the AiiA gene. The results of reverse transcript PCR analysis showed that the AiiA gene was expressed successfully in the yeast. Proteins extracted from YPDS showed the highest inhibition efficacy to E. carotovora compared with the other two mediums (YPD and LB) under tested conditions.

Quality Characteristics and FTIR Research of Amorphophallus konjac K. Koch Cultivated under Forest

[Objectives]This study aimed to evaluate the quality characteristics of Amorphophallus konjac K.Koch and study the tubers of A.konjac K.Koch by infrared spectroscopy and second derivative method.[Methods]Referring to industrial standards of China for agriculture and related documents,the quality characteristics of A.konjac K.Koch were determined;and using potassium bromide tableting method and Fourier transform infrared spectroscopy,the infrared spectrum and second derivative spectrum of A.konjac K.Koch were studied.[Results]The drying rate,total ash content,acid-insoluble ash content,water extract content,ethanol extract content and crude polysaccharide content of A.konjac K.Koch were above 14.00%,4.57%-11.78%,0.04%-4.87%,26.31%-36.98%,2.20%-7.95%and 40.25%-61.18%,respectively.The infrared spectra of A.konjac K.Koch of different origins were relatively close,and the differences were mainly in peak intensity.The peaks at 1642,1322,1241,1154,1022,863,770 and 576 cm-1 were the main specific peaks.The main component was konjac glucomannan.[Conclusions]FTIR technology is simple and quick,and is suitable for quality control and sample identification of A.konjac K.Koch.This provides a scientific basis for the quality control and comprehensive utilization of A.konjac K.Koch cultivated under forest.

Incorporation ofκ-carrageenan improves the practical features of agar/konjac glucomannan/κ-carrageenan ternary system

Three materials(agar,konjac glucomannan(KGM)andκ-carrageenan)were used to prepare ternary systems,i.e.,sol-gels and their dried composites conditioned at varied relative humidity(RH)(33%,54%and 75%).Combined methods,e.g.,scanning electron microscopy,small-angle X-ray scattering,infrared spectroscopy(IR)and X-ray diffraction(XRD),were used to disclose howκ-carrageenan addition tailors the features of agar/KGM/κ-carrageenan ternary system.As affirmed by IR and XRD,the ternary systems withκ-carrageenan below 25%(agar/KGM/carrageenan,50:25:25,m/m)displayed proper component interactions,which increased the sol-gel transition temperature and the hardness of obtained gels.For instance,the ternary composites could show hardness about 3 to 4 times higher than that for binary counterpart.These gels were dehydrated to acquire ternary composites.Compared to agar/KGM composite,the ternary composites showed fewer crystallites and nanoscale orders,and newly-formed nanoscale structures from chain assembly.Such multi-scale structures,for composites withκ-carrageenan below 25%,showed weaker changes with RH,as revealed by especially morphologic and crystalline features.Consequently,the ternary composites with lessκ-carrageenan(below 25%)exhibited stabilized elongation at break and hydrophilicity at different RHs.This hints to us that agar/KGM/κ-carrageenan composite systems can display series applications with improved features,e.g.,increased sol-gel transition point.

Effect of carboxymethyl konjac glucomannan coating on curcumin-loaded multilayered emulsion:stability evaluation

The stability against various environmental stresses of the curcumin-loaded secondary and tertiary emulsions that was emulsified by whey protein isolate(WPI)and coated by chitosan(CHI),carboxymethyl konjac glucomannan(CMKGM),or their combination through layer-by-layer assembly was investigated.Generally,the multilayered emulsions were destabilized in high Na Cl concentrations or medium p H that could interrupt the electrostatic interaction between the three polyelectrolytes or deprotonate CHI,indicating that electrostatic interaction played an important role in the stability of emulsions.Compared with the primary emulsion that was solely stabilized by WPI,extra coating with CHI and CMKGM generally increased the stability of the emulsion against repeated freezing-thawing,improved the retention of curcumin against heating,UV irradiation,and long-term storage,and the effects were more remarkable in the tertiary emulsion with CMKGM locating in the outmost layer.Since CMKGM has shown the colon-targeted delivery potency,the multilayered emulsions assembled by layer-by-layer deposition,especially the tertiary emulsion,could be used as an effective carrier for the targeted delivery of curcumin.

缅甸魔芋(Amorphophallus Muelleri)资源分布及产业基本概况

在缅甸13个含葡甘聚糖的野生魔芋种中,黄魔芋、白魔芋和红魔芋是当地民众习惯上按色泽进行区分的3类魔芋,每类又各包含几个种。其中,上缅甸以红魔芋和缅甸白魔芋居多,下缅甸则以黄魔芋和耐热型白魔芋(A.variabilis)为多。缅甸魔芋现仍以野生资源为主,加工品以干片为多,大宗产品出口中国,部分销往日本。因比较优势明显,日本已开始与缅方合作在缅规模化种植弥勒魔芋。

Rapid DNA Extraction Method from Amorphophallas.konjac and ISSR-PCR Amplification

[Objective]The research aimed to study the total DNA extraction methods of Amorphophallas.konjac.[Method]To investigate the optimum DNA extraction method,CTAB,SDS and new modified methods for isolating genomic DNA from Amorphophallas.konjac leaf were studied and the isolated DNAs were examined by ultraviolet absorption test,agarose gel electrophoresis and ISSR-PCR test for comparative analysis.[Result]The results showed that the new modified method was suitable for DNA isolation from Amorphophallas.konjac plants with high purity and yield;quality of DNA could meet ISSR-PCR requirement even extracted once by the new modified method.[Conclusion]The study provided basis for extracting high quality DNA sample,and offered the molecular genetics reference for exploring the genetic diversity of Amorphophallas.konjac.

Effects of Nitrogen, Phosphate and Potassium Fertilizers on Soft Rot of Konjac Based on Grey Correlation Analysis

[Objective] The effects of different application amounts of nitrogen, phos-phate and potassium fertilizers on soft rot of konjac were investigated in this study. [Method] The grey correlation analysis was adopted to evaluate the correlation be-tween the application amount of nitrogen, phosphate and potassium fertilizers and the occurrence of soft rot of konjac. [Result] The excessive application of nitrogen fertilizer would induce the occurrence of soft rot of konjac, but the application of potassium fertilizer had a good control effect on soft rot. [Conclusion] The applica-tion amount of nitrogen fertilizer should be control ed reasonably in the planting of konjac, but the application amount of phosphate and potassium fertilizer could be in-creased to some extent, reducing the occurrence of soft rot of konjac.

Studies on Hydrogen Bonding Network Structures of Konjac Glucomannan

In this paper, the hydrogen bonding network models of konjac glucomannan （KGM） are predicted in the approach of molecular dynamics （MD）. These models have been proved by experiments whose results are consistent with those from simulation. The results show that the hydrogen bonding network structures of KGM are stable and the key linking points of hydrogen bonding network are at the O（6） and O（2） positions on KGM ring. Moreover, acety has significant influence on hydrogen bonding network and hydrogen bonding network structures are more stable after deacetylation.

Synthesis and Characterization of Phosphated Konjac Glucomannan Hydrogels

Konjac glucomannan （KGM） was crosslinked with sodium tripolyphosphate （STPP） to synthesize hydrogels. The crosslinking reaction was confirmed by FT-IR. The results of degradation test show that the hydrogels retain the enzymatic degradation character of KGM and can be degraded for 74.45% in 5 days by cellulase E0240.

Study on Gel Formation Mechanism of Konjac Glucomannan

The transformation of molecular conformation after gelatinization of konjac glucomannan is characterized by means of GC, GPC, FT-IR, DSC, XRD and TEM. The results showed that the molecule of KGM had no branch, the monose composition and connecting type of the molecular chain had no change, the transformation of molecule weight was little, and its drying powder sample formed an evidently new crystalline region. The hollow double helix structure of KGM in hydrosol changed from stretch chain into intercross and entwisted after gelatinization. The gelatin formation mechanism of konjac glucomannan is thereby expounded.

Study on Molecular Chain Morphology of Konjac Glucomannan

The long-range structure of konjac glucomannan(KGM)is studied by using laser light scatter(LLS), gel permeation chromatography(GPC)and method of viscosidity. The weight-average molecular weight(Mw), root-mean-square ratio of gyration[(S2)1/2], second viral coefficient(A2)and multi-dispersion coefficient(Mw/Mn)are 1.04×106, 105. 0±0. 9 nm,(-1. 59±0.28)×10-3 mol ml g-2 and 1.015±0.003, respectively. Mark-Houwink equation is established as [η] = 5. 96×10-2Mw0.73 and the molecular chain parameters are as follows: ML=982. 82 nm-1, Lp = 27. 93 nm, d = 0. 74 nm, h = 0. 26 nm, L = l 054.11 nm. Further more molecular chain morphology of KGM is studied by using atom force microscope(AFM)and transmission electronic microscope(TEM), and the result shows that the KGM molecular is an extending semi-flexible linear chain without branch. Therefore, the image of molecular chain morphology confirms the deduction drawn by Mark-Houwink equation and molecular chain parameters.

Dynamics Study of the Influence of Temperature on Konjac Glucomannan Saline Solution’s Viscosity

Molecular dynamics （MD） method is adopted to simulate the conformation variations of konjac glucomannan （KGM） saline solution at different temperatures, and structurally analyze the trends and reasons of viscosity change in KGM saline solution with temperature. The experimental results have been analyzed to find out that the sum of formative hydrogen bonds decreases with the rise of temperature and the amount of intramolecular hydrogen bonds suddenly increases at 323 K. Besides, in terms of molecular orbital data obtained from simulation, we can know that hydrogen bonding energy also decreases with the rise of temperature. Therefore, we can predict the viscosity of KGM saline solution decreases gradually when rising the temperature.

Studies on Single Chain Structure of Konjac Glucomannan

The simulation is carried out by employing the method of molecular dynamics with the single chain of konjac glucomannan （KGM） in vacuum as the structural model to discuss the factors that affect the single chain structure, the dynamic structure of the chain and the acting forces that maintain the chain structure. The results show that the shape and stability of the chain are affected by the degree of polymerization. As for the KGM with high degree of polymerization, its chain presents random coiling state and its stability declines. Both before and after deacetylation in the process of dynamic motion, the chain of KGM presents random coiling state with periodic variation of extension and coil and demonstrates favorable flexibility, indicating acetyl is not the main factor that affects the shape of chain, whereas dihedral angle and static actions are respectively the key bonding and nonbonding acting forces that influence the single chain conformations in vacuum.

Analysis of Influential Factors of Konjac Glucomannan(KGM) Molecular Structure on Its Activity

Biological activity of konjac glucomannan is closely related to its structure,in particular to its high-level structure.Researches on the activity mechanism of konjac glucomannan are significant for revealing the mysteries of participation in life activity.In this paper,analysis of the effects of konjac glucomannan configuration and various factors on its structure and activity was conducted,mechanism of biological activity of konjac glucomannan was explored,and the hot research topic of konjac glucomannan was given.

Formation Sites and Microscopic Conformation Study on the Konjac Glucomannan Molecular Helices

In this work, the formation sites, helical parameters and hydrogen bond positions of Konjac glucomannan molecular helices were investigated using molecular dynamic simulation method. To our interest, the KGM chain is mainly composed by local left and right helix struetttres. The formation sites of KGM chain might locate at the chain-segments containing acetyl groups, and the left helix is the favorable conformation of KGM. Temperature-dependent molecule conformation study indicates that the right helix is dominant when the temperature is lower than 343 K, above which, however, the left helix is dominating （right helix disappears）. In addition, intramolecular hydrogen bonds in the left helix can be found at the -OH groups on C（2）, C（4） and C（6） of mannose residues; comparably, the intramolecular hydrogen bonds in the right helix can be mainly observed at the -OH groups on C（4） and C（6） of the mannose residues and C（3） of the glucose residues. In conclusion, molecular dynamic simulation is an efficient method for the microscopic conformation study of glucomannan molecular helices.

Hydrogen Bond Networks' QSAR and Topologica Analysis of Konjac Glucomannan Chains

Based on the knot theory and researching of network structures of glucomannan molecules, the polysaccharides were analyzed. The link prediction analysis is to further reveal the interactions between polysaccharides, to elaborate QSAR of polysaccharides, and to analyze the network conformation relationships among polysaccharides. We made a classification for glucomannan molecules based on the related domestic and international theories, and investigated their network structures and application prospects. The knot theory and the link predictions not only simplify the glucomannan microscopic descriptions but also play a guiding role in predicting and regulating the structures.