Faculty of Applied Sciences

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Poultry gut health : microbiome functions, environmental impacts, microbiome engineering and advancements in characterization technologies
(Springer Science and Business Media LLC, 2021-12-02) Aruwa, Christiana Eleojo; Pillay, Charlene; Nyaga, Martin M.; Sabiu, Saheed
The gastrointestinal tract (GIT) health impacts animal productivity. The poultry microbiome has functions which range from protection against pathogens and nutrients production, to host immune system maturation. Fluctuations in the microbiome have also been linked to prevailing environmental conditions. Healthy poultry birds possess a natural resistance to infection. However, the exploration of environmental impacts and other relevant factors on poultry growth and health have been underplayed. Since good performance and growth rate are central to animal production, the host-microbiome relationship remains integral. Prior to the emergence of metagenomic techniques, conventional methods for poultry microbiome studies were used and were low-throughput and associated with insufficient genomic data and high cost of sequencing. Fortunately, the advent of high-throughput sequencing platforms have circumvented some of these shortfalls and paved the way for increased studies on the poultry gut microbiome diversity and functions. Here, we give an up-to-date review on the impact of varied environments on microbiome profile, as well as microbiome engineering and microbiome technology advancements. It is hoped that this paper will provide invaluable information that could guide and inspire further studies on the lingering pertinent questions about the poultry microbiome.
In vitro efficacy of temperature and preservatives on fast food bacilli, and their antibiotic susceptibility profile
(2017-06-20) Aruwa, Christiana Eleojo; Akinyosoye, Felix Akinsola
Background and Objective: Species within the Bacillus genus are ubiquitous, and cause food infections and intoxications. Bacillus species are however rarely assayed for in convenience foods. Furthermore, consumer health protection as it relates to the keeping quality of convenience/fast foods (prior to sale to consumers), remain a subject of global concern. Therefore, this study focused on the in vitro efficacy of temperature and preservatives on fast food bacilli. Materials and Methods: A study of chemical preservative and thermal effect on test bacilli isolates was done, with spectrophotometric measurement of optical density at 600nm. Several concentrations of chemical preservatives (0.1-1% for potassium metabisulphite, sodium nitrite, sodium benzoate, and sorbic acid; and 1-10% for sodium chloride) were prepared. Test Bacillus species were subjected to the concentrations, incubated over a 72-hrs and readings taken periodically. Statistical analysis was carried out using one way ANOVA in SPSS version 15 package for separation of means at 95% confidence interval. Results: Findings showed that at 60oC holding temperature growth of test bacilli were effectively inhibited. Also, 8% sodium chloride, 0.3% sorbic acid, 0.4% sodium benzoate, 0.3% sodium nitrite and 0.4% potassium metabisulphite effectively inhibited all test bacilli. Antibiotic susceptibility results showed that B. megaterium and B. stearothermophilus were resistant to vancomycin, while B. cereus, B. subtilis and B. thuringiensis were susceptible to vancomycin. Other test bacilli were resistant to clindamycin except B. cereus and B. stearothermophilus. Conclusion: This study showed the importance of heat and chemical preservatives in the inactivation of Bacillus species. Holding temperatures (55-60oC) and/or preservatives (at minimum inhibitory levels) could improve the shelf life and quality of ready-to-eat foods prior to purchase, and ensure consumer health protection. Antibiotic susceptibility profile of test species would be efficacious in alleviating symptoms of Bacillus related food borne illness.
Characterisation of Opuntia phenolic extracts and enzymatic modification of selected compunds
(2019) Aruwa, Christiana Eleojo; Kudanga, Tukayi; Amoo, Stephen O.
Opuntia species are utilised as local medicinal interventions for chronic diseases and as food sources. The phytochemical profile varies within and across Opuntia species and has been related to differences in cultivar and geographical location. Macromolecular antioxidant (MA) fractions are also largely ignored from most conventional extractive processes compared to the well-known extractable polyphenol fractions. This study characterised subtropical spineless cladode, fruit pulp and peel extracts and selected phenolic compounds for enzymatic modification using a laccase from Trametes pubescens. MA extracts were also characterised in comparison with extractable fractions. The effects of drying methods and extraction solvent on extract yields and bioactivities were also studied. Extracts were assayed for phenolic content and antioxidant activities were determined using standard 2,2’-diphenyl-1-picrylhydrazyl (DPPH), 2,2,-azinobis3-ethylbenzthiazoline-6-sulfonic acid (ABTS) and ferric reducing antioxidant power (FRAP) assays. Antimicrobial activities and mode of antibacterial action were assessed against type-bacterial cultures. Minimum inhibitory concentration (MIC) values were recorded for the extracts and compounds. Compound profiling was achieved using liquid chromatography-time of flight-mass spectrometry (LC-TOF/MS) in negative ionisation mode. Antibacterial and antioxidant activities were higher in MA, hydrolysed and hydroalcoholic cladode and fruit extracts than in aqueous fractions. Ethanolic, methanolic and hexane extracts of freeze-dried Opuntia cladode, MA and peel samples showed higher total phenolic content, and in vitro antioxidant and antimicrobial activities than the oven-dried extracts. Cladode extracts inhibited growth of both Gram-positive and Gram-negative microorganisms (MIC range of 25 to 250 mg/mL). Likewise, fruit extracts inhibited both Gram-positive and Gram- negative microorganisms (MIC range of 2.5 to 18.75 mg/mL). Cladode and fruit extract profiles showed the presence of mainly phenolic acids and flavonoid derivatives. Isovitexin 7-O- xyloside-2"-O-glucoside, polyhydroxypregnane glycoside and neohancoside C in Opuntia cladode, and pinellic acid in Opuntia fruit were identified for the first time in this study. Some compounds, however, remained unidentified. Thereafter, selected Opuntia cladode and fruit phenolic compounds (isorhamnetin and luteolin) were used for enzymatic (laccase) transformation after preliminary screening reactions. Laccase-catalysed oxidation of luteolin in a monophasic system containing sodium acetate buffer (pH 5.0) and ethanol (50%, v/v) as co- solvent, resulted in the production of a dimer (m/z 569, M=570). Using a similar approach, oxidative coupling of isorhamnetin produced two main products, IP1 which was a dimer (m/z 629, M=630) and IP2 (m/z 457, M=458) which was most likely a result of coupling of an oxidative cleavage product and the isorhamnetin monomer. Dimers showed up to two-fold improvement in antioxidant and antimicrobial activities, compared to their respective substrates. The synthesised products showed a bactericidal mode of action as demonstrated by time-kill and bacterial cell integrity assays. The bactericidal action was further confirmed by scanning electron microscopy (SEM) which showed that treatment of bacterial cells with the synthesised compounds resulted in deformed, pitted, broken or fragmented cells, indicating strong bactericidal action. In conclusion, this study showed that Opuntia fruit pulp, peel and cladode extractable and MA extracts have potential as sources of phenolic compounds with antioxidant and antimicrobial activities. Laccase catalysis has potential to transform the phenolic compounds into coupling products with higher biological activities. The synthesised products have potential for application in the food, nutraceutical and other relevant industries.

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