Thesis
Detection and control of off-flavour compound-producing Streptomyces species in locally produced nuts
University of the Sunshine Coast, Queensland
Bachelor of Science (Honours), University of the Sunshine Coast, Queensland
2021
DOI:
https://doi.org/10.25907/00982
Abstract
Microbiota in soil is widely diverse and aids in many key aspects of plant health. Members of the phylum Actinobacteria are the most prominent part of the soil microbiota, more specifically the species within the genus Streptomyces of this phylum. Key functions of the Streptomyces species (or streptomycetes in general terms) include nutrient cycling and plant growth promotion. These species, however, can also produce volatile organic compounds (VOC), predominantly geosmin and 2-methylisoborneol (2-MIB) responsible for musty and mildew scents that are unpleasant to humans, negatively impacting the nut crop industry as the odorous nuts lose their market value. Nuts are one of the crops that are detrimentally impacted due to odorous streptomycete infestations. Bacterial viruses, called bacteriophages have been previously used successfully in agriculture and aquaculture to remove such odorous species they may therefore also be applied to the nut industry. To eliminate these compounds, the producer streptomycetes may be selectively removed from nut surfaces using Streptomyces-specific viruses called streptophages. The removal of Streptomyces species from nut surfaces can then be expected to minimize geosmin and 2-MIB production, therefore removing the unpleasant off-flavours and benefiting the nut industry. This study thus aimed to (1) first isolate and identify such odorous streptomycetes from different nut samples using molecular techniques (2) use streptophages to control the growth of these VOC producing streptomycetes deliberately introduced onto locally produced nuts, and (3) detect the VOC (2-MIB, dimethyl disulfide, and geosmin) differences in the nut samples deliberately infected with the streptomycete isolates and subsequently treated with or without the composite streptophage suspension using GC-MS. Eight streptomycetes isolated from seven different locally produced nut samples. Findings indicated a decrease in dimethyl disulfide and geosmin production after composite streptophage suspension application onto streptomycete infected nut samples, however, 2-MIB was not detected throughout the experiment duration which might be masked by other VOCs. The composite streptophage suspension studied under the TEM indicated that the phages belonged to the order Caudovirales within the Siphoviridae family. Overall, the study showed that streptophages can be an effective biocontrol agent to manage VOC production by steptomycetes present on nut surfaces.
Details
- Title
- Detection and control of off-flavour compound-producing Streptomyces species in locally produced nuts
- Authors
- Laura Grace Dionysius
- Contributors
- D. İpek Kurtböke (Principal Supervisor) - University of the Sunshine Coast, Queensland, School of Science, Technology and Engineering
- Awarding institution
- University of the Sunshine Coast, Queensland
- Degree awarded
- Bachelor of Science (Honours)
- Publisher
- University of the Sunshine Coast, Queensland
- DOI
- 10.25907/00982
- Organisation Unit
- School of Science, Technology and Engineering
- Language
- English
- Record Identifier
- 991186142602621
- Output Type
- Thesis
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