火龙果致腐菌的分离鉴定及生物拮抗防腐措施

Isolation and identification of pitaya spoilage fungi and the measures of biological antagonistic anticorrosion

【背景】红心火龙果在常温下贮藏3 d鳞片就会出现黄化、萎蔫、果柄发霉,贮藏8 d果实腐烂率高于55%,贮藏16d果实腐烂率达95.5%以上。【目的】对红心火龙果主要致腐微生物进行分离鉴定,并筛选出防腐效果最佳的拮抗菌株。【方法】采用传统纯培养法对红心火龙果的致腐微生物进行分离纯化;通过致腐菌回接火龙果试验,找出主要致腐菌;通过形态学鉴定、细菌16S rRNA基因和真菌的rDNA ITS鉴定、生物信息学分析对主要致腐微生物进行初步鉴定;利用11株芽孢杆菌作为供试拮抗菌株对火龙果进行生物防腐。【结果】从自然腐烂红心火龙果上共分离得到60株致腐菌,其中细菌占38.33%,真菌占61.67%。将60株致腐菌回接红心火龙果,常温贮藏27 d后发现有2株致腐菌导致火龙果腐烂率达100%。经鉴定为扩展青霉(P. expansum)和黑附球菌(E. nigrum),分别命名为BP15和BP25。经平板拮抗试验显示:解淀粉芽孢杆菌10075对菌株BP15和BP25的抑制率最显著,抑制率分别为60.59%和84.73%。采用稀释浓度为90%的10075过滤除菌上清液对BP15和BP25进行抑制,其抑制率分别为54.32%和90.00%,而上清液热处理后对BP15和BP25的抑制率分别降低1.30%和12.43%。以稀释浓度为90%的10075过滤除菌上清液喷涂火龙果,处理10 d的防腐效果均高于30%。【结论】火龙果具有极高的经济价值、营养价值和药用价值,其在常温下容易腐烂。研究可为火龙果常温贮藏保鲜提供一种有效的生物防腐方法。

[Background] The scales of red-hearted dragon fruit appear yellowing, wilting and moldy stalks when storing at room temperature for 3 days. The fruit rot rate is higher than 55% for 8 days, as well as 95.5% for 16 days. [Objective] To isolate and identify the main spoilage microorganisms and screen the antagonistic strains with the best antiseptic effect of red-hearted dragon fruit. [Methods] The spoilage microorganisms of red-hearted dragon fruit were isolated by pure culture. The dominant spoilage bacteria inoculated into dragon fruit were identified based on physiological and biochemical characteristics combined with sequences analysis of bacterial 16 S rRNA gene, fungal rDNA ITS and bioinformatic analysis. 11 Bacillus subtilis strains as the tested antagonistic strains were used as biological antisepsis for dragon fruit. [Results] A total of 60 spoilage bacteria were isolated from naturally decomposed red-heart dragon fruit, of which bacteria accounted for 38.33% and fungi accounted for 61.67%. All of them were inoculated into red-hearted dragon fruit, and then 2 spoilage bacteria causing 100% rotten were found when storing at room temperature for 27 days. The two spoilage bacteria were identified as P. expansum named BP15 and E. nigrum named BP25. The plate antagonism test showed that the inhibitory rate of Bacillus amyloliquefaciens 10075 to the BP15 and BP25 strains was the most significant, which reached 60.59% and 84.73%, respectively. The 10075 filtered sterile supernatant with a concentration of 90% was used to inhibit BP15 and BP25, of which the inhibitory rate were 54.32% and 90.00%, respectively. However, heat treatment of the supernatant resulted in the inhibitory rate of BP15 and BP25 decreasing by 1.30% and 12.43%, respectively. With 90% 10075 filter sterilization supernatant spraying on dragon fruit, the biological antisepsis characteristic was higher than 30% after 10 days’ treatment. The research provides an effective biological antisepsis method for storage and preservation of dragon fruit. [Conclusion] Dragon fruit has extremely high economic value, nutritional value and medicinal value, however it is easy to rot at room temperature. The research can provide an effective biological antisepsis method for the storage and preservation of dragon fruit at room temperature.