Sammanfattning

In this study, the microbiological food safety of using anaerobic digestate as a fertilizer in hydroponic production of vegetables was evaluated. The used anaerobic digestate was a liquid residue obtained from the digestion of food waste in the production of biogas. Replacing the customary inorganic fertilizer used in hydroponic production with this recycled fertilizer (biofertilizer) could allow for sustainable urban food production close to retailers and consumers. However, in striving for circular food production, it is vital that the food safety of utilizing recycled resources is ensured. Especially in the application of hydroponic farming, where the nutrient loop is shorter than on arable land, a microbiological food safety risk assessment is crucial when adopting new and recycled fertilizers. The biofertilizer based on anaerobic digestate was therefore studied with regard to its microbial community (16S rRNA gene amplicon sequencing) during production of vegetables in a hydroponic system. The biofertilizer was also challenge tested with food borne pathogens (Salmonella enterica, Listeria monocytogenes and Bacillus cereus). Furthermore, the microbial activity of the biofertilizer was studied using isothermal calorimetry. The results showed that the microbial community of the biofertilizer changed distinctly through a necessary initial nitrification process, and that the most abundant genus was Mycobacterium. Deliberate contaminations with 5 log10 CFU mL−1 of either S. enterica or L. monocytogenes in the nitrified biofertilizer were no longer detectable with selective plating after 48 h of incubation at 20 °C. Selective plating for B. cereus revealed that the biofertilizer contained low levels (∼10 CFU mL−1) of the bacterium, and an inoculation of 5 log10 CFU mL−1 B. cereus decreased to these levels within 24 h of incubation at 20 °C. Analysis of the microbial activity of the biofertilizer indicated that the biofertilizer does not seem to support microbial activity without the addition of an external nutrient source that contains an accessible carbon source and trace elements. The type of biofertilizer investigated in this study is thus regarded as microbiologically safe for use in hydroponic cultivation. The constant presence of viable B. cereus, however, emphasizes the fundamental importance of continuous risk assessment in case of any modifications or supplementations of the biofertilizer, since it clearly can act as a reservoir for bacterial endospores.

Nyckelord

Circular food production systems; Food-borne pathogens; Isothermal calorimetry; Microbial community analysis; Microbial food safety risk assessment; Waste recovery

Publicerad i

Journal of Cleaner Production
2022, Volym: 333, artikelnummer: 130239

SLU författare

• Bergstrand, Karl-Johan

  • Institutionen för biosystem och teknologi, Sveriges lantbruksuniversitet
    

• Asp, Håkan

  • Institutionen för biosystem och teknologi, Sveriges lantbruksuniversitet
    

• Hultberg, Malin

  • Institutionen för biosystem och teknologi, Sveriges lantbruksuniversitet
    

Associerade SLU-program

Food Waste


Globala målen

Säkerställa hälsosamma liv och främja välbefinnande för alla i alla åldrar
Avskaffa hunger, uppnå tryggad livsmedelsförsörjning och förbättrad nutrition samt främja ett hållbart jordbruk
Säkerställa hållbara konsumtions- och produktionsmönster


UKÄ forskningsämne

Trädgårdsvetenskap/hortikultur
Livsmedelsvetenskap
Miljö- och naturvårdsvetenskap


Publikationens identifierare

DOI: https://doi.org/10.1016/j.jclepro.2021.130239

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/115122