Detection of Talaromyces macrosporus and Talaromyces trachyspermus by a PCR assay targeting the hydrophobin gene

Abstract

Talaromyces species are typical fungi capable of producing the heat‐resistant ascospores responsible for the spoilage of processed food products. Hydrophobins, which are unique to fungi, are small secreted proteins that form amphipathic layers on the outer surface of fungal cell walls. In this study, species‐specific primer sets for detecting and identifying Talaromyces macrosporus and Talaromyces trachyspermus were designed based on hydrophobin gene sequences. A conventional polymerase chain reaction (PCR) assay using these primer sets produced species‐specific amplicons for T. macrosporus and T. trachyspermus. The detection limit for each primer set was 100 pg template DNA. This assay also detected fungal DNA extracted from blueberries inoculated with T. macrosporus. Other heat‐resistant fungi, including Byssochlamys, Neosartorya and Talaromyces species, which cause food spoilage, were not detected in PCR amplifications with these primer sets. Furthermore, a conventional PCR assay using a crude DNA extract as the template also yielded amplicons specific to T. macrosporus and T. trachyspermus. The simple and rapid PCR assay described herein is highly species‐specific and can reliably detect T. macrosporus and T. trachyspermus, suggesting it may be relevant for the food and beverage industry. Significance and Impact of the Study The heat‐resistant ascospores of Talaromyces macrosporus and Talaromyces trachyspermus are responsible for food spoilage after pasteurization. Traditional methods for detecting fungal contamination based on morphological characteristics are time‐consuming and exhibit low sensitivity and specificity. In this study, a conventional polymerase chain reaction (PCR) assay based on hydrophobin gene sequences was developed for the specific detection of T. macrosporus and T. trachyspermus. This detection method was simple, rapid and highly specific. These results suggest that the conventional PCR assay developed in this study may be useful for detecting T. macrosporus and T. trachyspermus in raw materials and processed food products.

Occurrence of Heat-Resistant Mold Ascospores in Pineapple and Sugarcane Field Soils in Thailand

“…Supporting our results, HRMs belonging to Talaromyces and Penicillium have been detected in fruit and fruit products with low frequency [ 22 ]. The major Talaromyces species, such as T. macrosporus , T. flavus , T. trachyspermus, and T. bacillisporus , are generally associated with spoiled fruit products [ 36 , 38 ]. Penicillium species are widely distributed in soil, indoor environments, and food products [ 39 ].…”

Heat-resistant moulds: Assessment, prevention and their consequences for food safety and public health

“…Penicillium glabrum has been separated into an enormous diversity of items, including cheese, nuts, and bottled mineral water (Nevarez et al 2010). Talaromyces trachyspermus has been separated from heat-processed cheeses, canned strawberries and tea-based refreshments (Yamashita et al 2019). Ochratoxin A (OTA) mycotoxin is found in coffee beans, red wine, spices, cereals and nuts (Calado et al 2014).…”