Bacterial cellulose-based antifouling materials have been produced by incorporation of silver nanoparticles for broad-spectrum antimicrobial activity. Three variations of silver nitrate (AgNO3) to reducing agent concentrations have been tried to vary the silver nanoparticle dimension. The formation of silver nanoparticles was also evidenced by the X-ray diffraction, and the crystallite size was found to decrease with increase in NaBH4 concentration. AgBC composites having < 2% (W/W) of silver exhibited 99.9% antimicrobial activity which was sustained up to 72 h against spoiled food derived mixed microbial culture. On the other hand, only 90% activity was observed with colloidal AgNPs due to aggregate formation. Composites displayed superior antimicrobial activity than colloid with equivalent amount of silver. Food stuff was protected from microbial spoilage for 30 days when stored in AgBC nanocomposites, whereas spoilage was noticed within 15 days for food stuff stored in regular polythene bag. Therefore, the AgBC composite having < 2% silver can be used as a lining of regular food packaging material to extend shelf life till 30 days. Toxicity due to high amount of silver can be prevented with these composites and can be safely used in healthcare applications such as food packaging, wound dressing, hospital bed lining and surgical apparels.

Broad-spectrum antimicrobial activity of bacterial cellulose silver nanocomposites with sustained release

This study evaluates the single and combined usage of chitosan (2% w/v) and rhamnolipid (2% w/v) as edible coatings to extend the shelf life of sweet oranges stored at 25 °C for 8 weeks. Physiochemical, microbial and sensory analysis of the oranges was conducted during ambient storage. The combined treatment of chitosan and rhamnolipid coating on oranges significantly delayed a loss in chlorophyll quality, malondialdehyde, weight loss, soluble solids content, titratable acidity, vitamin C content and delayed the loss of firmness during the 8 weeks of storage. The combined chitosan–rhamnolipid coating significantly increased the activities of superoxide dismutase, catalase, and peroxidase, as well as inhibited the generation of superoxide free radicals and the growth of mesophilic bacteria, yeast and mould.

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Prolonging the shelf life of ‘Agege Sweet’ orange with chitosan–rhamnolipid coating

The tomato leaf miner (Tuta absoluta) destroyed tomato plants in seven of the Northern states in Nigeria, and has been found in two other states in the South in 2016. The study assessed the incident of the tomato leafminer attack using a questionnaire survey in one of the affected states, for a case study of the problem. A short literature review on bio-ecology of T. absoluta was also conducted, and responses to questionnaires were presented. It appeared that knowledge of farmers on pests and management procedures was poor. The results showed that farmers were not properly oriented on pest reporting, and many farmers were unaware of the existence of government pest support programs. Pest monitoring programs and post attack response systems were found inadequate. Many farmers perceived that the pest was new while some respondents reported that similar attacks occurred on their farms in the previous year. Most respondents declined to answer questions on the possibility of agro-bioterrorism being the cause of the attack. We found a lacuna in the government policy which could be potentially exploited by agro-terrorists to inflict attack on crops in a new dimension, but there is no evidence of agro-terrorism in relation to attack on tomato by T. absoluta in Nigeria. The findings could be useful in the development of pest mitigating strategies in agro-dependent developing countries.

	Key words: Tuta absoluta, agro-terrorism, climate change, pest development, tomato.

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The tomato leafminer (Tuta absoluta) (Lepidoptera: Gelechiidae) attack in Nigeria: effect of climate change on over-sighted pest or agro-bioterrorism?

This study investigated the health risks from tomato consumption with regard to microbial contaminants and heavy metal content of fresh and stale tomatoes (Lycopersicon esculentum) sold in selected markets within Port Harcourt metropolis, Nigeria. Standard microbiological procedures were employed for the determination of microbial density while flame atomic absorption spectrometry was used for heavy metal analysis. Results showed values of chromium, copper, manganese, zinc, total heterotrophic bacteria and total fungi ranging from 0.396 to 0.896 mg/kg, 0.602 to 2.434 mg/kg, < 0.001 to 1.770 mg/kg, 0.110 to 2.048 mg/kg, 2.300 × 106 CFU/g to 7.167 × 106 CFU/g and 1.467 × 105 CFU/g to 2.767 × 105 CFU/g, respectively. There were significant variations (p < 0.05) across the different markets for all test parameters except total fungi. Cadmium and lead were not detected in the tomatoes. The estimated daily intake of metals from consumption of tomatoes in the study areas was less than the maximum tolerable daily intake. The total hazard quotient and health index were < 1, an indication of no associated adverse health effect. Among the metals studied, there was no carcinogenic risk of lead and cadmium given they were below measurable detection limit; however, the ingestion of tomatoes containing chromium in the study area was within permissible predicted lifetime risks of carcinogens (10−6–10−4), while the microbial density was far higher than acceptable (≤ 103 CFU/g), but close to tolerable (104–105 CFU/g) for total fungi limits in food as specified by the International Commission on Microbiological Specifications for Foods. The high microbial density indicates unsanitary practices by local vendors. As a result, it is important to frequently assess microbial load and potential metal contamination of tomatoes to forestall potential health concerns linked with their consumption, especially the immuno-toxicological effects of metal toxicity.

Microbial and heavy metal hazard analysis of edible tomatoes (Lycopersicon esculentum) in Port Harcourt, Nigeria

Amylases (EC 3.2.1.1) are cellwall degrading enzymes associated with the pathogenicity of microorganisms in the spoilage
of tomato fruits. The use of amylase in many industries has made it very important to optimize production process to
achieve maximum yields. Screening and partial purification of Amylase from Aspergillus niger isolated from tomato
(Lycopersicon esculentum Mill.) fruits was studied. Amylase producing fungi were isolated from fresh tomatoes kept at
ambient temperature (28±1˚C). Isolates were characterized on the basis of their morphological and cultural techniques. Partial
purification of amylase was carried out by ammonium sulphate precipitation. The enzyme activity was determined and
optimum conditions were obtained. The molecular weights of the crude and partially purified Amylase were determined by SDS
PAGE method. A total of five isolates were obtained using basic screening technique for amylase activity, one of the isolates
(Isolate code F2) exhibited maximum amylase activity. The fungi isolate code F2 was identified as Aspergillus niger.
Optimum conditions for Amylase AMY F2 were ascertained at pH 6.0; temperature 30°C; substrate concentration of
0.3mg/ml, and time of heating of less than 10min. The molecular weights of the crude and partially purified Amylase AMY F2
were found to be 55kDa and 35kDa respectively by SDS PAGE method. Microorganisms had been an encouraging means of
economical production of enzymes in large scale for the food and drug industry.

/pdf/screening-and-partial-purification-of-amylase-from-3domywym88.pdf

Screening and partial purification of amylase from Aspergillus Niger isolated from deteriorated tomato ( Lycopersicon Esculentum mill.) fruits

This study was carried out to isolate and identify pathogenic microorganisms associated with deterioration of tomato fruits. Fruit samples of infected and non-infected tomatoes were collected from two open markets, Oja-Oba and Sabo in Osogbo, Nigeria. Each of the tomato was cut and the liquid content inoculated on nutrient agar and potato dextrose agar, incubated at 37 0C and 25 0C, respectively, and observed from 24 hours to 5 days, after which different colonies obtained were identified using slide culture technique. Two bacteria, Staphylococcus aureus and Bacillus spp, as well as two fungi Aspergillus flavus and Rhizopus stolonifer were observed in the tomato samples in both markets. Prevalence indices revealed that isolated pathogens is higher at Sabo market than Oja-Oba market. Pathogenicity tests also revealed that both of bacteria and fungi caused fruit decay. Consumers’ awareness on potential health hazards of consuming relatively cheaper and pathogen contaminated spoilt fruits should be intensified.

https://www.entomoljournal.com/archives/2016/vol4issue1/PartF/4-1-12.1.pdf

Odunayo Olawuyi J

Papers

Microorganisms causing post-harvest tomato (Solanum lycopersicum L.) fruit decay in Nigeria