Biocontrol of postharvest gray and blue mold decay of apples with Rhodotorula mucilaginosa and possible mechanisms of action

The efficacy of Rhodotorula mucilaginosa against postharvest gray mold, blue mold and natural decay development of apples and the possible mechanisms involved were investigated. The decay incidence and lesion diameter of gray mold and blue mold of apples treated by R. mucilaginosa were significantly reduced compared with the control fruits, and the higher concentration of R. mucilaginosa, the better the efficacy of the biocontrol. R. mucilaginosa also significantly reduced the natural decay development of apples following storage at 20 °C for 35 days or at 4 °C for 45 days followed by 20 °C for 15 days. Germination and survival of spores of Penicillium expansum and Botrytis cinerea were markedly inhibited by R. mucilaginosa in an in vitro test. Rapid colonization of the yeast in apple wounds was observed whether stored at 20 °C or 4 °C. In apples, the activities of peroxidase (POD) and polyphenoloxidase (PPO) were significantly induced and lipid peroxidation (malondialdehyde (MDA) content) was highly inhibited by R. mucilaginosa treatment compared with those of the control fruits. All these results indicated that R. mucilaginosa has great potential for development of commercial formulations to control postharvest pathogens on fruits. Its modes of action were based on competition for space and nutrients with pathogens, inducement of activities of defense-related enzymes such as POD, PPO and inhibition of lipid peroxidation (MDA content) of apples, so as to enhance the resistance and delay the ripening and senescence of apples.     

苯并噻二唑结合罗伦隐球酵母对桃果采后青霉病的控制

研究了拮抗酵母菌罗伦隐球酵母与植物诱导剂苯并噻二唑(BTH)结合使用控制桃果青霉病的效果。结果显示,罗伦隐球酵母与100μg/mL的BTH结合使用时,不仅其生防效力显著提高,还可以显著提高桃果的抗性相关酶活性,包括过氧化物酶(POD)和过氧化氢酶(CAT),并且抑制了丙二醛(MDA)含量的增加。因此,BTH与罗伦隐球酵母结合使用,集成了生物防治酵母和植物生长调节剂的生物双重活性,可能成为防治桃果采后病害的一个新途径。      

Methyl jasmonate enhances biocontrol efficacy of Rhodotorula glutinis to postharvest blue mold decay of pears

The effect of Rhodotorula glutinis treatment alone or in combination with methyl jasmonate (MeJA) in controlling blue mold decay, the natural fungal decay of pears and the postharvest quality parameters including fruit firmness, total soluble solids, titratable acidity, and ascorbic acid were investigated. The combination of methyl jasmonate (200 μM) and R. glutinis (1 × 10⁸ CFU/ml) was a more effective approach to reduce the disease incidence and lesion diameter of blue mold decay of pears than the application of MeJA or R. glutinis alone after incubation for 7 d at 20 °C. The natural fungal decay of pears treated with the application of R. glutinis combined with MeJA resulted in reduced average decay incidence of 10.42% or 4.16%, respectively, compared with 27.17% or 20.83% in the control fruits following storage at 20 °C for 15 d or 4 °C for 60 d followed by 20 °C for 15 d. The combined treatment did not impair quality parameters of fruits under both conditions.     

低温等离子体处理模式对冷藏南美白对虾中假单胞菌的抑菌效果及机理研究

摘 要：目的 探究低温等离子体(cold plasma, CP)处理模式对冷藏南美白对虾中常见荧光假单胞菌(Pseudomonas fluorescens)的抑菌效果及其作用机制。方法 通过CP直接处理和循环处理P. fluorescens,研究了两种处理模式下臭氧含量动态变化对P. fluorescens的生长曲线、细胞活力,生物膜形成、细胞壁、细胞膜完整性和南美白对虾菌落总数及假单胞菌数等指标的影响。结果 两种处理模式在CP处理3 min或3 cycles后,包装内臭氧含量达到最高值,分别为(850±10) mg/m3和(874±20) mg/m3。CP循环处理模式使得臭氧含量随处理循环数递增,因此获得更长的臭氧存在时间从而具有更大的抑菌能力。P. fluorescens生长曲线表明CP处理使得菌体延迟期变长且对数生长期推迟。此外,CP处理后的P. fluorescens细胞活力显著下降(P<0.05),CP-1 min,CP-3 min和CP-3 cycles组的细胞活力分别为33.03%、5.90%和4.82%。同时相比CP-3 min组,CP-3 cycles组的P. fluorescens生物膜OD值下降27.61%。碱性磷酸酶(alkaline phosphatase, AKP)活性和核酸蛋白泄漏量结果表明,细胞壁和细胞膜完整性受损可能是P. fluorescens失活的直接原因。对虾保鲜测试结果证实,贮藏第6 d,CP-3 cycles组虾体中的菌落总数和假单胞菌数相比CP-3 min组分别降低了58.02%和79.54%。结论 CP循环处理模式通过延长对臭氧与对虾的暴露时间,提高了对P. fluorescens的灭活效果,同时还具有更优越的保鲜能力。本研究为开发基于CP技术的新型保鲜技术应用提供了理论参考。 关键词：低温等离子体;荧光假单胞菌;抑菌机制;保鲜     

Biocontrol ability and action mechanisms of Aureobasidium pullulans GE17 and Meyerozyma guilliermondii KL3 against Penicillium digitatum DSM2750 and Penicillium expansum DSM62841 causing postharvest diseases

Epiphytic yeasts were isolated from different cultivars of apples and lemons and identified by a combination of PCR-RFLP of 5.8S rRNA region and sequencing of D1/D2 domain of the 26S rRNA gene. Among 69 isolates, Aureobasidium pullulans GE17 and Meyerozyma guilliermondii KL3 strains showed the greatest antagonistic activity against two significant apple and lemon postharvest pathogens, Penicillium expansum DSM62841 (blue mold) and Penicillium digitatum DSM2750 (green mold), after preliminary screening. Yeasts were applied as single and mixed cultures with two different cell concentrations of 10⁶ and 10⁸ cells/ml in the present study. It was determined that antagonistic activity of two yeast strains studied emerged with a combination of several mechanisms of action including competition for space and nutrients, production of volatile organic compounds (VOCs), secretion of extracellular lytic enzymes and inhibition of fungal spore germination. The highest inhibition of mycelial growth on P. expansum DSM62841 and P. digitatum DSM2750 (83.4% and 74.7%, respectively) was achieved by utilization of single culture of A. pullulans GE17. Otherwise, the application of mixed culture at the ratio of 10⁸ cells/ml inhibited spore germination of both pathogens from 86% to 95%. Results of this study suggest that an increase in yeast cell concentrations positively affected their biocontrol activity against blue and green molds. According to the results, employing single culture of M. guilliermondii KL3 did not exhibit effective antagonistic activity against blue and green molds. However, utilization of A. pullulans GE17 alone and mixed culture showed succesfull controlling against both P. expansum DSM62841 and P. digitatum DSM2750.     

兰州百合青霉病病原菌分离鉴定及生物学特性研究

目的 探索引起兰州百合采后贮藏期间青霉病的主要病原菌,研究其生物学特性。方法 从自然发病的青霉病病害组织中分离纯化得到引起兰州百合青霉病的主要病原,通过形态学和分子生物学技术对其进行鉴定,并对影响该病原菌生长发育的温度、光照、pH、碳氮源、湿度进行分析。结果 引起新鲜兰州百合采后贮藏期间青霉病的主要病原菌为唐菖蒲青霉(Penicillium gladioli)。该菌在60℃下致死,温度20℃、pH中性偏碱、24 h黑暗,碳源为麦芽糖,氮源为尿素时,菌落生长最好;在温度为25℃、pH中性偏碱、24 h黑暗,碳源为蔗糖,氮源为酵母时,产孢量最多。结论 确定了引起兰州百合采后贮藏期间青霉病的主要病原菌为唐菖蒲青霉,并明确了其最适温湿度、pH、碳源、氮源、光照条件及致死温度等生物学特性,为进一步有效控制兰州鲜百合采后青霉病的发生提供理论基础。     

苯乳酸对荧光假单胞菌基于细胞膜损伤和DNA破坏的双靶位抑菌机制

荧光假单胞菌是导致冷藏食品腐败变质常见的嗜冷菌,抑制荧光假单胞菌的生长繁殖对延长冷藏食品货架期和提高食品安全性具有重要意义.本实验通过测定最小抑菌浓度(minimum inhibitory concentration,MIC)和时间-抑菌曲线考察苯乳酸对荧光假单胞菌的抑菌活性,从细胞膜电势、细胞膜渗透性和完整性、细胞超...     

荧光假单胞菌和热杀索丝菌对低温贮藏期间猪肉品质变化的影响

为研究荧光假单胞菌和热杀索丝菌与猪肉品质变化的相关性,测定了在4 ℃下贮藏猪肉的微生物菌落数、pH值、色泽（L*、a*、b*值）、质构特性、总糖含量、总挥发性盐基氮（total volatile basic nitrogen,TVB-N）值和硫代巴比妥酸反应物（thiobarbituric acid reactive substances,TBARS）值以及通过扫描电子显微镜观察猪肉肌纤维微观结构的变化。结果表明,在冷藏期间,微生物菌落数、pH值、TVB-N值、TBARS值等随着猪肉冷藏时间延长而上升,而总糖含量、L*值、a*值、硬度、咀嚼性均呈降低趋势。同时,研究发现猪肉冷藏过程中微生物的生长繁殖使其肌纤维结构发生明显变化。猪肉理化品质变化与微生物的种类和生长速率相关,热杀索丝菌的致腐败能力高于假单胞菌。相关性分析结果表明,菌落数、pH值、总糖含量、TVB-N值、TBARS值与冷藏时间密切相关,其中微生物菌落数与冷藏时间的相关性最高,可作为冷藏猪肉品质评价和货架期预测的监测指标。     

荧光假单胞菌噬菌体对大西洋鲑贮藏过程中品质变化情况研究

目的 探究大西洋鲑在4℃贮藏过程中, 外源添加荧光假单胞菌及其噬菌体影响大西洋鲑品质变化相关的常见指标的变化规律, 为噬菌体在实际食品作为保鲜剂的应用提供科学依据。方法 采用色差值、菌落总数(Total viable count, TVC)、挥发性盐基氮(Total volatile basic nitrogen, TVB-N)、质构、硫代巴比妥酸(Thiobarbituric acid, TBA)、pH、剪切力、持水性等致腐能力指标对冷藏温度(4℃)条件下大西洋鲑的新鲜度变化进行综合评价。结果 4℃贮藏期间, 初期微生物生长迅速且数量变化明显, 噬菌体vB_PF_Y1-MI的加入使得鱼肉中TVC下降了大约0.07 lg ( CFU·g-1 ); 大西洋鲑TVB-N含量整体变化趋势明显呈指数型增长, pH值均呈现先下降后上升的变化趋势; 添加荧光假单胞菌组的大西洋鲑TBA值和失水率增加程度较为明显, 经噬菌体处理后增加程度有所降低。结论 噬菌体vB_PF_Y1-MI的加入, 能够降低大西洋鲑鱼肉脂质氧化速率, 可以延缓其腐败变质, 从而延长大西洋鲑保质期。     

腐败希瓦氏菌和荧光假单胞菌对冷藏凡纳滨对虾虾汁品质的影响

为研究腐败希瓦氏菌（Shewanella putrefaciens）、荧光假单胞菌（Pseudomonas fluorescens）的致腐败能 力以及两种菌之间的相互关系,将这两种菌株的单一培养物和混合培养物分别接种至无菌虾汁中,于（4±1）℃下 培养8 d,测定虾汁中菌落数及总挥发性盐基氮（total volatile basic nitrogen,TVB-N）、氨基酸、腐胺、肌浆蛋白 和挥发性物质含量的变化情况。结果表明：混合接菌组中S. putrefaciens和P. fluorescens的最大菌落数分别为8.85、 8.26（lg（CFU/mL））,均高于单独接菌组。且混合接菌组的TVB-N含量和腐胺含量明显高于两组单一接菌组。 在虾汁培养物中S. putrefaciens比P. fluorescens更容易生长繁殖,这两种菌存在协同作用,可相互促进彼此的生长和 加速凡纳滨对虾虾汁的腐败。     

热空气复合茉莉酸甲酯处理对杨梅果实采后腐烂和品质的影响

目的 分析热空气复合茉莉酸甲酯(methyl jasmonate, MeJA)处理对杨梅果实采后腐烂和品质的影响。方法 将“乌种”杨梅在48 °C下进行10 μmol/L MeJA的熏蒸处理, 随后在20 °C下贮藏3 d或者1 °C下贮藏5、10 d、15 d后再20 °C贮藏1 d以模拟货架条件, 贮藏期间或结束后测定果实发病率以及硬度、可滴定酸(titratable acid, TA)、可溶性固形物(Total Soluble Solid, TSS)、维生素C和总酚等品质指标。同时, 采用芽管离体培养法测定该复合处理对Verticicladiella abietina(杨梅轮帚霉)孢子萌发和菌丝生长的影响。结果 10 μmol/L MeJA处理对V. abietina孢子萌发无明显抑制作用, 但可显著抑制病原菌菌丝的生长; 48 °C热空气处理则可显著抑制病原菌孢子萌发和菌丝生长。单一热空气或茉莉酸甲酯处理均可抑制杨梅果实采后贮藏期间绿霉病发病率, 但两者复合处理较单一处理更为显著的抑制了杨梅果实病害发生, 且经复合处理的杨梅果实其硬度、TA、TSS、维生素C和总酚含量均显著高于单一处理果实。结论 热空气复合茉莉酸甲酯处理可通过抑制V. abietina的生长从而控制杨梅果实采后腐烂并同时延缓果实品质下降, 从而为该复合处理的实际应用提供理论依据。     

Efficacy of preharvest and postharvest Candida sake biocontrol treatments to prevent blue mould on apples during cold storage

This study compared the biocontrol efficiency of preharvest and postharvest applied yeast cells of Candida sake to apples (cv. Golden Delicious) wounded before and after harvest and inoculated with Penicillium expansum prior to cold storage conditions in two seasons, 1994/95 and 1995/96. The establishment of populations of C. sake during this period also was determined. In both years, postharvest treatment with the antagonist resulted in significant (P<0.05) and effective control of Penicillium rot whether pre- or postharvest wounds were made. Maximum disease control achieved, in terms of incidence and severity, was greater than 80% reduction in lesion diameter and 50% reduction in the incidence of lesions. However, preharvest application of the antagonistic yeast at a concentration of 3·10⁶ CFU/ml was less effective against Penicillium rot than postharvest treatment. No advantages in biocontrol were observed when apples were treated with the yeast antagonist both pre- and postharvest. Candida sake population levels during cold storage of apples receiving only preharvest application of the antagonist decreased prior and more rapidly than levels in apples receiving a postharvest application. High populations of C. sake were present in postharvest-treated apples, even after 90 days in cold storage.