Adhezija plesni vrste Penicillium expansum

Pavlovič, Brina (author), Jeršek, Barbka (mentor)

Plesni vrste Penicillium expansum povzročajo gnilobo številnih živil, med katerimi so te plesni najpogostejši kontaminanti jabolk. Ker plesni vrste P. expansum lahko tvorijo patulin, predstavljajo tudi tveganje za varnost živil. Glavni namen dela je bil določiti sposobnost njihove adhezije, saj večina strokovne literature opisuje bakterijsko adhezijo, medtem ko so raziskave adhezije plesni redke. V prvem delu smo metodo določanja adhezije z barvilom kristal vijolično (KV) optimizirali z izbiro gojišča (sladni agar in krompirjev agar) in starosti konidijev (7 in 10 dni) za pripravo inokuluma ter določitvijo valovne dolžine (570 nm in 584 nm) za kvantifikacijo adheriranih plesni. V drugem delu smo proučevali adhezijo plesni vrste P. expansum tako, da smo preverili vplive izbranih intrinzičnih in ekstrinzičnih dejavnikov. Rezultati so pokazali, da je za spremljanje adhezije boljše, ča uporabimo inokulum pripravljen iz 10 dni stare kulture, saj je bila adhezija tu veliko večja ter da gojišče, na katerem rastejo plesni za pripravo inokuluma, ne vpliva na adhezijo. Pri primerjavi rezultatov dobljenih z meritvami absorbanc sproščenega KV pri različnih valovnih dolžinah, razlik nismo zaznali. Med intrinzičnimi dejavniki smo ugotovili, da ima velik vpliv na adhezijo začetno število konidijev, saj je bila adhezija največja pri 108 K/ml (K: konidiji), ter čas adhezije plesni vrste P. expansum (adhezija po 20 urah je bila večja kot po 40 urah), medtem ko vrsta seva (tipski sev P. expansum ŽMJ 497, divji sev P. expansum ŽMJ 464) ni bistveno vplivala na adhezijo. Plesni vrste P. expansum dobro rastejo na številnih materialih, ki se uporabljajo tudi v živilski industriji, zato smo primerjali njihovo adhezijo na različnih površinah (polistiren, polipropilen, polietilen visoke gostote, polietilen tereftalat, steklo in nerjaveče jeklo). Največjo adhezijo smo določili na površini polistirena. Adhezijo plesni vrste P. expansum na vseh površinah smo opazovali tudi z vrstično elektronsko mikroskopijo in ugotovili, da so morfološke lastnosti povezane z vrsto površine. Zaključimo lahko, da je metoda barvanja s KV primerna kot preliminarna metoda določanja adhezije plesni in da se plesni vrste P. expansum dobro adherirajo na površino, vendar so potrebne nadaljnje raziskave.

• Language: Slovenian
• Keywords: plesni, Penicillium expansum, adhezija plesni, biofilm plesni, kvar, mikotoksini, varnost živil, embalažni materiali, površine
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: BF - Biotechnical Faculty
• Place of publishing: Ljubljana
• Publisher: [B. Pavlovič]
• Year: 2022
• PID: 20.500.12556/RUL-140483
• UDC: 579.24+579.26:582.282.123.2
• COBISS.SI-ID: 121941763
• Publication date in RUL: 15.09.2022

Secondary language

• Language: English
• Title: Adhesion of Penicillium expansum

Abstract

Strains of Penicillium expansum cause rotting of many foods, among which they are the most common contaminant of apples. As P. expansum can form patulin it is also a food safety risk. The main purpose was to determine P. expansum adhesion ability, since most scientific literature describes bacterial adhesion, while moulds adhesion is rare. In the first part, the method of determining adhesion with crystal violet dye (CV) was optimized by choosing medium (malt agar and potato agar) and age of conidia (7 and 10 days) for preparation of inoculum and determining the wavelength (570 nm and 584 nm) for adherence quantification. In the second part, we studied the adhesion of P. expansum by checking the influence of selected intrinsic and extrinsic factors. Results showed that for adhesion monitoring it is better to use an inoculum prepared from a 10-day-old culture, as the adhesion was much greater, and that the culture medium on which the moulds grow prior inoculum preparation, does not affect adhesion. When comparing the results obtained by measuring the absorbance of released CV at different wavelengths no differences were found. Among the intrinsic factors, we found out that initial number of conidia had a major influence since adhesion was highest at 108 K/ml (K: conidia), and adhesion time (adhesion after 20 h was greater than after 40 h), while strain (P. expansum ŽMJ 497 type strain, P. expansum ŽMJ 464 wild strain) did not affect adhesion. P. expansum strains grow well on many materials that are also used in food industry and we compared adhesion on different surfaces (polystyrene, polypropylene, high-density polyethylene, polyethylene terephthalate, glass and stainless steel). The maximum adhesion was determined on the polystyrene. Adhesion of P. expansum on surfaces was also observed by scanning electron microscopy and it was found that the morphological properties are related to the type of surface. We can conclude that the KV staining method is suitable as a preliminary method for determining mould adhesion and that P. expansum adhere well to the surface, but further research is needed.

• Keywords: fungi, Penicillium expansum, adhesion of fungi, fungal biofilm, spoilage, mycotoxins, food safety, packaging materials, surfaces