Examination of novel Aureobasidium pullulans isolates dominating apple microflora and assessing their potential for apple juice spoilage

Abstract

There is very little up to date information regarding apple microflora so in the current study we decided to address that issue and assess whether dominant fungi which reside in fruit might spoil apple juice. Microorganisms were isolated from apples of Koksa Górska harvested in the middle of October in 2016 and 2017. Identification of isolates was based on the sequencing of ribosomal DNA. Some isolates were characteristic for a particular year but in both years apple microflora was dominated by Aureobasidium pullulans. Based on phylogenetic analysis it was stated that only one isolate (LW81) was closely related to strains which are already described in available databases. All other isolates collected in the current study differed significantly from sequences stored in databases, tending to form a common cluster. It was possible to predict secondary structure of ITS2 region only for the isolate LW81, while we managed to establish the length and location of 5.8S gene in Rfam database for all sequences. A. pullulans is known exopolysaccharide producer so obtained microorganisms were tested for their ability to synthesise those substances on Czapek-Dox agar. The strain which proved to be the most significant exopolysaccharide producer (isolate LW14) was inoculated in the sterilised apple juice at three different initial cell number (100, 1000 and 10,000 cfu/ml) and subjected to pasteurisation. In all cases pasteurisation eliminated fungal growth effectively, therefore A. pullulans strains should not pose any risk to the quality of pasteurised apple juices.

Dried Biomass of Arthrospira platensis Inhibits Growth of Aureobasidium pullulans LW14 and Some Bacteria When Added to Unpasteurised Apple Juice

“…We adjusted the number of fungal cells to that which was found in freshly harvested apples. Previously we demonstrated that the most abundant species in apple of Koksa Górska variety was Aureobasidium pullulans so in the current study we chose A. pullulans LW14 strain that was proved to be potent exopolysaccharide producer [10] and could potentially spoil unpasteurised juice.…”

“…In the current study we narrowed down the dose of A. platensis biomass in an apple juice which could inhibit fungal growth and determined which fraction of cyanobacterium biomass participated in this phenomenon. For that purpose we carried out experiments in sterilised apple juice inoculated with Aureobasidium pullulans LW14 that was the representative of the species dominating fungal microflora and which demonstrated the highest synthesis of exopolysaccharides [10]. In the last research stage we verified obtained results by adding selected cyanobacterium fraction to the unpasteurised apple juice.…”

Identification and antibiotic pattern analysis of bacillary dysentery causing bacteria isolated from stool samples of infected patients

“…The neighbor-joining evolution method inferred the evolutionary history (Dash et al 2015 ). The maximum sequence differences were 0.75, and the sequences were labeled with taxonomic names (Sequence ID) (Wajda et al 2018 ).…”

Application of Bioactive Coatings with Killer Yeasts to Control Post-Harvest Apple Decay Caused by Botrytis cinerea and Penicillium italicum

“…The killer yeast strain of Wickerhamomyces anomalus CBS 1982 was provided from the CBS-KNAW Collections, Westerdijk Fungal Biodiversity Institute (Utrecht, The Netherlands). The killer yeast strain of Pichia membranifaciens LW26 was isolated from apple fruits of cultivar Koksa Górska (Łososina, Poland), which was harvested in the middle of October 2016 [21]. Similarly, Penicillium italicum LW75 was isolated from diseased apple fruits of the cultivar Szara Reneta (Grójec, Poland), harvested in the middle of October 2016.…”