Vol.:(0123456789) 1 3 Journal of Thermal Analysis and Calorimetry https://doi.org/10.1007/s10973-020-10011-7 Estimation of microbiological contamination of maize seeds using isothermal calorimetry Andrzej Skoczowski 1  · Sebastian W. Przemieniecki 2  · Jakub Oliwa 3  · Monika Kula‑Maximenko 4  · Magdalena Rys 4  · Iwona Stawoska 1  · Stanisław Karpiński 5 Received: 3 July 2019 / Accepted: 29 June 2020 © The Author(s) 2020 Abstract The storage of maize seed intended for industrial purposes in foil silo bags is associated with microbiological contamina- tion of the material by bacteria and fungi. This results in the loss of a part of the raw material or its deterioration and causes fnancial losses. In this paper, the relationship between the number of microorganisms colonizing maize seeds as well as changes in heat fow has been proved. For this purpose, the heat fow and total metabolic heat emission values (total heat) were analyzed. Calorimetric measurements of seed samples were made using the TAM III isothermal calorimeter. The seed samples with the same heat fow curves shape were homogenized, and microbial DNA was isolated from them. The quantita- tive real-time polymerase chain reaction (qPCR) was performed for detecting the main group of microorganisms colonizing maize seeds. It has been shown that in the case of seeds less afected by Bacillus and fungi (including yeast), the heat fow (in the range of 0–360 min) has a falling shape, while for more infected it grows almost linearly. The more infected maize seeds also show signifcantly higher values of total heat emission. The described research can be used to quickly assess the degree of seed contamination. Keywords Bacillus spp. · Bacteria · Fungi · Heat fow · Zea mays Introduction Long-term storage of maize seeds (intended for example for the production of bioethanol) in plastic silo bags creates problems of technological and economic nature. Microbial contamination of the material by bacteria and fungi present on the seed coat negatively afects the fermentation pro- cesses and deterioration of the quality of the fnal product (e.g., presence of mycotoxins, ammonia, butyric acid). In addition, the reduction in the technological quality of seeds, and consequently the loss of a part of the raw material, causes signifcant fnancial losses. For this reason, moni- toring the quality of the biological material taken is very important [1, 2]. Microbiological analysis of environmental samples based on microbial cultures (for example on Petri dishes) is time- consuming and their results are often ambiguous. A better alternative is molecular methods such as: DNA markers, metagenomics analysis, DNA barcoding, molecular phyloge- netic or using PCR. However, the disadvantage of methods based on DNA analysis is the inability to recognize live cells from dead ones as well as the variable efciency of DNA extraction. An additional aspect is the need to design primers and probes and optimize the hybridization conditions [3, 4]. For this reason, we have decided to use isothermal calorim- etry to monitor the degree of microbial contamination of seeds, without the need of long-term and expensive analysis. * Andrzej Skoczowski andrzej.skoczowski@up.krakow.pl 1 Institute of Biology, Pedagogical University of Cracow, Podchorążych 2, 30-084 Kraków, Poland 2 Department of Entomology Phytopathology and Molecular Diagnostics, University of Warmia and Mazury in Olsztyn, Prawocheńskiego 17, 10-720 Olsztyn, Poland 3 Department of Chemistry and Biochemistry, Institute of Basic Sciences, University of Physical Education, Jana Pawła II 78, 31-571 Kraków, Poland 4 The Franciszek Górski Institute of Plant Physiology Polish Academy of Sciences, Niezapominajek 21, 30-239 Kraków, Poland 5 Department of Plant Genetics, Breeding and Biotechnology, Warsaw University of Live Sciences, Nowoursynowska 159, 02-776 Warsaw, Poland