Introduction: Essential oils (EOs) have been demonstrated as efficacious against B. cinerea. However, the underpinning enzymatic and proteomic mechanism for these inhibitory effects is not entirely clear.Methods: Thus, this study examined the effects of lemon (Le) and lemongrass (Lg) EOs (individually and in combination) against B. cinerea based on enzymatic and proteomic analyses. Proteomics data are available via ProteomeXchange with identifier PXD038894.Results and discussion: Both EOs (individually and in combination) displayed abilities to induce scavenging as observed with the reduction of H2O2. Measured malondialdehyde (MDA) and superoxide dismutase (SOD) activity were increased in all EOs treated B. cinerea mycelia compared to the control. Ascorbate peroxidase (APX) activity was highest in Lg treated B. cinerea (206% increase), followed by combined (Le + Lg) treatment with 73% compared to the untreated control. Based on GC-MS analysis, the number of volatile compounds identified in lemon and lemongrass EOs were 7 and 10, respectively. Major chemical constituent of lemon EO was d-limonene (71%), while lemongrass EO was a-citral (50.1%). Based on the interrogated LC-MS data, 42 distinct proteins were identified, and 13 of these proteins were unique with 1, 8, and 4 found in Le-, Lg-, and (Le + Lg) EOs treated B. cinerea, respectively, and none in control. Overall, 72% of identified proteins were localized within cellular anatomical entity, and 28% in protein-complexes. Proteins involved in translation initiation, antioxidant activity, protein macromolecule adaptor activity and microtubule motor activity were only identified in the Lg and (Le + Lg) EOs treated B. cinerea mycelia, which was consistent with their APX activities.

Background: Postharvest pathogens Botrytis cinerea and Penicillium expansum causes significant postharvest deterioration of fresh fruit, resulting in economic losses globally. Essential oils (EOs) are safe fungal biodeterioration alternatives compared to chemical fungicides. The aim of this study was to characterise and evaluate the additive and/or synergetic effects of lemon (Le‐), lemongrass (Lg‐), and peppermint (P‐EOs) against mycelial growth and spore germination of B. cinerea and P. expansum.Results: GC–MS analysis depicted 7, 10 and 10 compounds being the major component for Le‐, Lg‐ and P‐EOs, respectively. Most abundant compound being δ‐limonene (71%), α‐citral (50.1%), and menthyl acetate (48%) in Le‐, Lg‐ and P‐EOs, respectively. In vitro investigation showed significant inhibition against mycelial growth and spore germination of B. cinerea and P. expansum with a MIC of 5 and 10 mg/L, respectively. P. expansum was more susceptible to the EOs compared to B. cinerea. The concentrations causing 50% reduction (EC₅₀) in mycelial growth for P. expansum were 4, and 9 mg/L for P‐EO and Le‐EO, respectively. At the lowest concentration (0.62 mg/L), volatile phase treatment for P‐ and Lg‐EOs showed 100% inhibitory effects against all fungal mycelial growth compared to contact phase with ≈30% and 60% inhibitory effects, respectively, against P. expansum.Conclusions: Combination of essential oils showed stronger antifungal efficacy compared to individuals. EOs were more effective in volatile phase than direct contact at low concentrations. This shows the potential of using EOs in fogging treatments.

The management of ethylene during postharvest storage is of critical importance to fresh produce wholesalers and retailers. The management of ethylene is an important determinant of the quality and shelf life of fresh fruit and vegetables. Ethylene blocking action and ethylene removal via potassium permanganate, photocatalytic oxidation and ozonation have been extensively researched and applied on a commercial scale to manage the impacts of ethylene postharvest. However, these techniques have certain inherent limitations that make them ineffective for long-term postharvest applications. This review therefore focuses on ethylene removal strategies during postharvest handling, and characterisation of the merits and demerits of such strategies. In addition, it provides an overview of emerging techniques such as photolysis, photocatalytic oxidation and ozone-assisted catalytic oxidation, as alternatives for ethylene management along the postharvest value chains. The intent of this review was to guide the development of more effective ethylene management technologies for long-term application in the South African fruit industry.

While bioleaching is a proven technology for the efficient recovery of base metals from sulphide minerals, its sustenance is dependent on the continuous availability of ferric ion, Fe³⁺, in soluble form, in bioleach liquor. However, the solubility of ferric ion is low at higher pH thus resulting in the formation of various types of ferric ion precipitates, which decreases leaching efficiency by trapping the leached metals in solution through an adsorption. The effect of initial solution pH on the surface properties of ferric ion precipitates was investigated with a view to establish a relationship between operational pH and surface charge on precipitate and to relate this to the precipitates metal adsorption properties. Ferric ion precipitates recovered from a typical biooxidation process were characterized by XRD, SEM, PSD and zeta potential. Potassium-hydronium jarosite were the main phases identified by X-ray diffraction (XRD) analyses. The SEM results revealed that the precipitates had smooth surfaces with development of sharp edges on the precipitates formed at high pH. The precipitates formed at higher pH had less positive charge and scavenged more copper ions due to the high electrostatic attraction forces. The results from this study revealed that surface charge on a precipitate can give an indication of its metal adsorption capacity and that in order to prevent metal loss and improve extraction efficiency, solution conditions should be maintained such that the resulting precipitates have high positive surface charge to promote high electrostatic repulsion forces.