Natasa Hulak

Prof. Dr. Natasa Hulak

orcid

Research Focus & Metrics

Academic Career Length

10Years (2017-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 January 2017 in Food Technology and Biotechnology
Verified
Journal Article
Open access
Mirna Mrkonjić FukaMirna Mrkonjić Fuka
Mirna Mrkonjić Fuka
AMAna Zgomba Maksimovic
Ana Zgomba Maksimovic
ITIrina Tanuwidjaja
Irina Tanuwidjaja
Natasa HulakNatasa Hulak
Natasa Hulak
Michael SchloterMichael Schloter
Michael Schloter
In this study, prevalence, biotechnological and safety profiles of 588 Enterococcus isolates isolated from raw milk and Istrian cheese during different stages of ripening were analyzed. Despite the low and variable presence of enterococci in milk ((3.65±2.93) log CFU/mL), highly comparable enterococcal populations were established after 30 days of cheese ripening ((7.96±0.80) log CFU/g), confirming Enterococcus spp. as a major part of the core microbiota of Istrian cheese. The dominant species were E. faecium (53.8%) and E. faecalis (42.4%), while minor groups, consisting of E. durans (2.84%) and E. casseliflavus (0.95%), also occurred. A pronounced intraspecies variability was noticed based on molecular fingerprinting, with 35 strains (genotypes) detected. Most of the genotypes were farm-specific with one third being shared between the farms. This genotype variability reflected particular differences of Istrian cheese production, mainly variable salt concentration, ripening temperature and air humidity as well as microclimatic or vegetation conditions. There was considerable variation between the strains of the same species regarding wide range of biotechnologically important traits as well as their ability to survive in simulated gastrointestinal conditions. A considerable number of strains were resistant to critically important antibiotics such as tetracycline (43.56%), erythromycin (35.79%) and vancomycin (23.48%). Polymerase chain reaction-based detection did not identify any of the common genetic determinants for vancomycin and erythromycin resistance; for tetracycline tetM gene was detected. The presence of virulence genes including agg, efaAfs, gelE, cylM, cylB, cylA, esp, efaAfm, cob and cpd was frequently recorded, especially among E. faecalis strains.

25 March 2021 in Molecules
Verified
Journal Article
Open access
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Jana Šic ŽlaburJana Šic Žlabur
Jana Šic Žlabur
MBMarko Brajer
Marko Brajer
SVSandra Voca
Sandra Voca
AGAnte Galić
Ante Galić
Sanja RadmanSanja Radman
Sanja Radman
Natasa HulakNatasa Hulak
Natasa Hulak
Spices are a popular food of plant origin, rich in various phytochemicals and recognized for their numerous properties. The aim of the study was to evaluate the antioxidant and antimicrobial activity, as well as the content of specialized metabolites, of aqueous extracts of three spice species––garlic (Allium sativum L.), ginger (Zingiber officinalle L.) and turmeric (Curcuma longa L.)––prepared by green extraction methods. Ultrasound treatment increased the chromaticity parameter b value of turmeric and ginger extracts, thus indicating a higher yellow color predominantly due to curcuminoids characteristic of these species. Ultrasound-assisted extraction significantly increased the content of total soluble solids, phenolic compounds, total carotenoids and vitamin C. The temperature of the system was also an important factor, with the highest (70 °C) conditions in ultrasound-assisted extraction having a positive effect on thermolabile compounds (vitamin C, phenolics, total carotenoids). For example, turmeric extract treated with ultrasound at 70 °C had up to a 67% higher vitamin C content and a 69.4% higher total carotenoid content compared to samples treated conventionally at the same temperature, while ginger extracts had up to 40% higher total phenols. All different concentrations of spice extracts were not sufficient for complete inhibition of pathogenic bacterial strains of Salmonella, L. monocytogenes and S. aureus; however, only garlic extracts had an effect on slowing down the growth and number of L. monocytogenes colonies. Spice extracts obtained by ultrasonic treatment contained a significantly higher level of bioactive compounds and antioxidant capacity, suggesting that the extracts obtained have significant nutritional potential and thus a significant possibility for phytotherapeutic uses.

30 June 2026 in Journal of Hazardous Materials
Verified
Journal Article
Open access
XYXunzhe Yang
Xunzhe Yang
YLYunjie Li
Yunjie Li
Ping YunPing Yun
Ping Yun
DJDongqing Jia
Dongqing Jia
Natasa HulakNatasa Hulak
Natasa Hulak
GSGeng Sun
Geng Sun
"Hidden hunger" and heavy metal contamination in agricultural products pose critical challenges to agricultural security, with microbial inoculants offering a potential pathway for synergistic mitigation. This study conducted a systematic meta-analysis from 442 studies, exploring the regulation and mechanisms of microbial inoculants on crop essential and toxic heavy metal contents. Results indicate that microbial inoculants significantly enhance crop growth, increasing essential heavy metals accumulations including Cu, Fe, Mo, and Zn by 10-20%, while reducing the toxic metals contents like Cd and Pb by 20%. These processes are influenced by inoculant type, crop species, and soil conditions. The reduction of toxic metals is attributed to microbial diversity-mediated synergistic regulation. Machine learning results indicated that soil pH, total nitrogen, and organic matter were key factors influencing the essential heavy metals accumulation after inoculation. Organic matter, available phosphorus, and pH were key factors influencing the toxic heavy metals accumulation. Under toxic metal stress, inoculation could alter photosynthetic pigment dynamics and stabilize photosynthesis. Exogenous essential metals inhibited microbial enhancement of soil microbial diversity and saturated plant uptake, yielding no synergistic benefits when combined. Microorganisms only achieve decoupling of Fe, Mn, Mo, and toxic heavy metals. Since Cu, Ni, and Zn exist as ions or in weakly chelated forms, they remain at risk of co-transportation. This study provides an unbiased assessment of feasibility and limitations of microbial inoculants in improving food nutritional quality, alleviating "hidden hunger," and ensuring agricultural product safety.

18 August 2026 in Agronomy
Verified
Journal Article
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Marko VincekovićMarko Vinceković
Marko Vinceković
KGKarla Gašparić
Karla Gašparić
NJNenad Jalšenjak
Nenad Jalšenjak
Natasa HulakNatasa Hulak
Natasa Hulak
Microorganism inoculants are becoming increasingly essential in sustainable agriculture because they improve nutrient availability, promote plant growth, inhibit disease, and increase crop tolerance to environmental stresses. Nonetheless, their field performance is frequently hampered by poor storage survival, low rhizosphere establishment, and susceptibility to harsh climatic conditions. Encapsulation technologies provide an effective solution by encapsulating microbial cells in a biodegradable matrix, extending shelf life, increasing vitality, and allowing for controlled release in the soil. This review focuses on four agriculturally significant microorganisms: Azotobacter chroococcum, Azospirillum brasilense, Pseudomonas brassicacearum, and Trichoderma harzianum. Their modes of action, including nitrogen fixation, phytohormone synthesis, pathogen inhibition, and stimulation of plant defense responses, are reviewed alongside recent advances in encapsulation strategies. Alginate-based formulations and proposed potential multi-species microbial consortia are discussed as promising strategies for improving inoculant performance. However, the successful development of multifunctional potential microbial formulations requires further investigation of microbial compatibility, formulation stability, synchronized release behaviour, and long-term storage performance before broad agricultural implementation can be achieved.

24 July 2025 in Applied Sciences
Verified
Journal Article
Open access
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DLDarija Bendelja Ljoljić
Darija Bendelja Ljoljić
MBMelita Boroša
Melita Boroša
Ivica KosIvica Kos
Ivica Kos
LCLuka Cvetnić
Luka Cvetnić
Ivan VnučecIvan Vnučec
Ivan Vnučec
VTVESNA JAKI TKALEC
VESNA JAKI TKALEC
Following hygiene standards in milk production is essential for making high-quality sour cream, especially when using traditional methods that rely on raw milk. The aim of this study was to determine the physicochemical, microbiological, and sensory quality of artisanal sour cream samples collected from major marketplaces in the wider Zagreb area. On average, the samples contained 27.99% milk fat, 3.30% protein, 34.29% dry matter, 6.51% fat-free dry matter and 3.00% lactose, with considerable variability observed across all components. Microbiological analysis revealed the presence of Staphylococcus aureus in 35.30% of the samples, Enterobacteriaceae in 76.47%, Escherichia coli in 94.11%, Bacillus spp. in 23.53%, and yeasts in 100% of the samples. Listeria monocytogenes and Salmonella spp. were not detected. The sensory analysis of the textural properties showed significant variability in firmness, adhesiveness, viscosity, creaminess, and fizziness. Samples with higher milk fat and dry matter content were rated better for creaminess, viscosity and mouth firmness. Flavour assessments, particularly for cream and diacetyl notes, also varied widely among samples. These findings highlight the complexity of sour cream’s sensory attributes and the significant influence of ingredient composition and processing techniques on appearance, aroma, texture, taste, and flavour. Principal component analysis (PCA) with Varimax rotation simplified the data structure and identified key dimensions of quality variation. Principal component analysis (PCA) revealed that the first principal component (PC1) effectively discriminated the cream samples based on sensory attractiveness and indicators of spoilage and highlighted the association between off-flavour and microbial contamination with inferior characteristics. The second principal component (PC2) captured the differences in physicochemical characteristics and showed a gradient from richer, creamier samples with higher fat content to those with lower acidity and higher freshness.

31 August 2022 in Šumarski list
Verified
Journal Article
Closed access
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DUDamir Ugarkovic
Damir Ugarkovic
ITIvica Tikvić
Ivica Tikvić
KPKrešimir Popić
Krešimir Popić
PŠPetar Šutalo
Petar Šutalo
VRVibor Roje
Vibor Roje
IGIvana Grgurić
Ivana Grgurić
Odumiranjem stabala mijenjaju se stanišne prilike u šumskom ekosustavu, uslijed čega dolazi do promjene mikroklime i mikrobiološke aktivnosti tla. Cilj ovoga istraživanja je utvrditi razlike u mikroklimi staništa te u enzimatskoj aktivnosti šumskog t...