Aidee Kamal Khamis

The potential hazards of Aspergillus sp. in foods and feeds, and the role of biological treatment: A review

The contamination of food and feed by Aspergillus has become a global issue with a significant worldwide economic impact. The growth of Aspergillus is unfavourable to the development of food and feed industries, where the problems happen mostly due to the presence of mycotoxins, which is a toxic metabolite secreted by most Aspergillus groups. Moreover, fungi can produce spores that cause diseases, such as allergies and asthma, especially to human beings. High temperature, high moisture, retarded crops, and poor food storage conditions encourage the growth of mold, as well as the development of mycotoxins. A variety of chemical, biological, and physical strategies have been developed to control the production of mycotoxins. A biological approach, using a mixed culture comprised of Saccharomyces cerevisiae and Lactobacillus rhamnosus resulted in the inhibition of the growth of fungi when inoculated into fermented food. The results reveal that the mixed culture has a higher potential (37.08%) to inhibit the growth of Aspergillus flavus (producer of Aflatoxin) compared to either single culture, L. rhamnosus NRRL B-442 and S. cerevisiae, which inhibit the growth by 63.07% and 64.24%, respectively.

Reduction of soil acidity for agriculture activities in Malaysian ultisols by rhodopseudomonas palustris

The potential of the phototrophic bacterium, Rhodopseudomonas palustris (R. palustris), to reduce the acidic soil pH of Malaysian Ultisols (Bungor Series) was investigated. The R. palustris was first adsorbed onto the dried pineapple leaves (DPL) before being applied. The most suitable broth condition for the bacterium that could be adsorbed onto the DPL was identified. Different conditions and amounts of R. palustris adsorbed onto the DPL % (w/w) were tested in soils where the soil pH was monitored. It was found that the maximum cell adsorption onto the DPL was obtained using an initial cell concentration of 1.5 x 107 colony-forming units (CFU) mL-1, at pH 8.0 with the ionic strength of 5 mmolL-1 ammonium nitrate (NaNO3). The R. palustris was adsorbed onto the DPL surface area of 64.33 A. The acidic soil was treated with R. palustris adsorbed onto the DPL by direct application. The calcium carbonate (CaCO3) was introduced as a benchmark to reduce the soil acidity. The results showed that, with the application of R. palustris adsorbed on 5.0 % (w/w) of DPL, the soil pH was improved from 4.9 to more than 6.0 after 12 d of application. This improved soil pH will make the soil more applicable for agricultural activity.

Assessment of compost stability using single and mixed culture in a static semi-closed fed-batch reactor

Different microbial inoculums are expected to affect the degradation and stability of different compost materials. The results tend to vary more significantly in an open system due to the varied ambient conditions (temperature, moisture and air-borne microbial). To minimise such variation and avoid low reproducibility of the data, the present work was performed in a static semi-closed fed-batch reactor (SSCFBR) for better control of the composting process. The thermophilic Bacillus coagulans (BC) and the commercial effective microorganisms (EM) were used as the microbial inoculum (MI) in the SSCFBR. Distilled water was used in place of the MI for the control experiments. The mixture of chicken dung (CD), wooden husk (WH), and rice husk (RH) were used as the compost materials. The MI was inoculated into the compost bed in the SSCFBR (15 L working volume) at the same initial optical density (OD) of 0.8 and the initial volume of 800 mL with a forced aeration of 0.4 L/min. The parameters for the assessment of compost stability included the temperature, moisture content, oxygen uptake rate (OUR) and carbon dioxide emission rate (CER). BC showed comparable or better results to that achieved by the commercial EM. The temperature profile for both composts showed similar patterns where the highest peak of temperature was recorded within 1 d of composting (slightly higher for BC, 55 ± 0.8 °C and 47 ± 0.8 °C for EM). Such thermophilic temperature profile has not been observed in the control. The initial moisture content was set similar for all composts (44.5 ± 0.7 %). The moisture content declined slightly different for both MI compost (to 39.0 ± 0.6 % for BC and 36.6 ± 1.2 % for EM). Both composts showed very similar trend in the OUR. A higher evolution rate of carbon dioxide (CO2) was observed for the compost with BC for the first three days (0.06 ± 0.014 g/mol) as compared to that by EM (0.02 ± 0.007 g/mol). On the 4th d of composting, the production of CO2 in EM compost showed a near constant value (0.008 ± 0.002 g/mol) but the BC compost showed the rate of 0.06 ± 0.01 g/mol the 5th d and declined to 0.02 ± 0.004 g/mol on the 7th d. For both composting cases, the highest rate of CO2 was observed at the highest peak of temperature. The SSCFBR has been designed and could be used to facilitate the assessment of compost stability in a closed system with improved reproducibility of the data for composting.