NRU :: Browsing by Author "Byakika, Stellah"

Browsing by Author "Byakika, Stellah"

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Adopting traditional fermented foods as carriers for probiotics: The case of Obushera and Lactobacillus rhamnosus yoba
(Nutrition & Food Science, 2019) Muzira Mukisa, Ivan; Byakika, Stellah; Meeme, Rehema; Wacoo, Alex Paul; Sybesma, Wilbert
Traditional fermented products can be adopted as probiotic carriers. This study was aimed at evaluating the potential of using Obushera, a traditional sorghum beverage from Uganda, as a carrier for Lactobacillus rhamnosus yoba. Design/methodology/approach – Probiotic Obushera was produced by fermenting sorghum malt with Lb. rhamnosus yoba 2012 and Streptococcus thermophilus C106 at 30 °C and at room temperature (21°C-25 °C) for 24 h. Acidity, pH, total soluble solids and microbial counts were monitored. Consumer acceptability and purchase index of probiotic Obushera were compared to four commercial non-probiotic brands. Shelf stability of probiotic Obushera was determined by monitoring changes in pH, acidity, soluble solids, microbial counts and consumer acceptability during refrigerated storage. Findings – Lactobacillus rhamnosus yoba 2012 multiplied and lowered the pH of Obushera from 5.3 to < 4.0 (p < 0.0001) whilst increasing acidity from 0.21 to 0.46 per cent (p < 0.0001) in 9 h at 30 °C. Consumer acceptability varied with Obushera brand (p < 0.0001). The overall acceptability score of probiotic Obushera (score of 6.4 = like slightly) was similar to that of the two most acceptable commercial brands (scores of 5.8 and 6.6). Acidity, pH and Lb. rhamnosus counts of probiotic Obushera varied within 0.6 per cent –1.05 per cent (p < 0.0001), 3.3–3.4 (p < 0.0001), and 8.2-9.2 log cfu/ml (p < 0.0001), respectively during two months of storage. The overall acceptability of probiotic Obushera (scores of 6.9-7.8) did not change significantly during storage (p = 0.185). Practical Implications – Traditional fermented foods such as Obushera can be adopted as carriers of probiotic microorganisms. Originality/value – Use of commercial probiotic strains in traditional fermented foods is a novel approach that can be adopted to improve safety of traditional fermentations and health of consumers.
Antimicrobial Activity of Lactic Acid Bacteria Starters against Acid Tolerant, Antibiotic Resistant, and Potentially Virulent E. coli Isolated from a Fermented Sorghum-Millet Beverage
(International Journal of Microbiology, 2019) Byakika, Stellah; Muzira Mukisa, Ivan; Mugabi, Robert; Muyanja, Charles
Bacterial contamination of fermented foods is a serious global food safety challenge that requires effective control strategies. -is study characterized presumptive E. coli isolated from Obushera, a traditional fermented cereal beverage from Uganda. -ereafter, the antimicrobial effect of lactic acid bacteria (LAB) previously isolated from Obushera, against the E. coli, was examined. -e presumptive E. coli was incubated in brain heart infusion broth (pH � 3.6) at 25°C for 48 h. -e most acid-stable strains were clustered using (GTG)5 rep-PCR fingerprinting and identified using 16S rRNA sequencing. E. coli was screened for Shiga toxins (Stx 1 and Stx 2) and Intimin (eae) virulence genes as well as antibiotic resistance. -e spot-on-the-lawn method was used to evaluate antimicrobial activity. Eighteen isolates were acid stable and are identified as E. coli, Shigella, and Lysinibacillus. -e Stx 2 gene and antibiotic resistance were detected in some E. coli isolates. -e LAB were antagonistic against the E. coli. Lactic acid bacteria from traditional fermented foods can be applied in food processing to inhibit pathogens. Obushera lactic acid bacteria could be used to improve the safety of fermented foods.
Application of refrigerated and frozen sorghum malt slurries in preservation of starter cultures of traditional fermented cereal-based beverages - a case of Obushera from Uganda
(Research Square, 2020) Muzira Mukisa, Ivan; Serwanga, Arnold; Byakika, Stellah
Industrial production of traditional fermented beverages in developing countries is limited by lack of commercial starter cultures. Saccharomyces (S.) cerevisiae MNC 21Y and Lactobacillus (L.) plantarum MNC 21 were identi􀂦ed as starter cultures for a Ugandan cereal beverage, Obushera. However, they are commercially unavailable due to lack of affordable appropriate propagating and preservation methods. In this study the starters were propagated in sorghum malt slurries (30 °C for 24 h) and stored at 5 °C and − 18 °C for 90 days. Viability and fermentation ability of the cultures was monitored. Results Viability was higher for starters stored at 5 °C (S. cerevisiae: 6 log cfu/g and L. plantarum: 7–9 log cfu/g during 90 days) than those at -18 °C (S. cerevisiae: 2 cfu/g and L. plantarum: 4 log cfu/g after 30 days). Refrigerated starters acidi􀂦ed Obushera (pH ≤ 4.5) faster (10–20 h) than frozen ones (18–24 h). Refrigerating the starters in sorghum malt slurries preserves them for at least three months. This provides an affordable option for starter commercialization and industrial production of traditional fermented foods.
Characterizing Selected Sorghum Grain Varieties and Evaluating the Suitability of Their Malt Extracts for Cultivating Microbial Biomass
(International Journal of Food Science, 2021) Byakika, Stellah; Muzira Mukisa, Ivan; Byenkya Byaruhanga, Yusuf
Microbial biomass is cultivated for different technological applications including food processing, medicine, waste management, and research. The conventional growth media used are generally expensive thus necessitating the development of more affordable alternatives. In this study, four sorghum grain varieties, SESO 1, SESO 3, Epuripur, and Eyera, and their malt extracts were characterized which is aimed at determining their suitability for growing microbial biomass. The varieties had kernel length, kernel width, kernel thickness, and thousand kernel weigh equivalent to 3.8-4.3 mm, 3.2-4.5 mm, 2.4-2.8 mm, and 12.4-20.2 g, respectively. SESO 1 and Epuripur had corneous endosperm textures whereas those of SESO 3 and Eyera were intermediate and floury, respectively. Varieties had germinative energies > 90% and total defects < 8%. SESO 3 had the highest (p < 0:05) crude protein (10:8 ± 0:3%) and dietary fiber (22:5 ± 0:4%) whereas Epuripur had the highest (p < 0:05) starch (81:6 ± 0:0%) and crude fat (2:9 ± 0:1%). There was no significant difference (p > 0:05) in the ash contents (2:1 ± 0:0%). The total sugars, free amino nitrogen, condensed tannins, and pH of the malt extracts were 106-116 g/L, 70-78 mg/L, 0.1-0.6 mg/mL, and 5.5-5.7, respectively. The composition of the sorghum malt extracts suggests their potential for use in cultivating microbial biomass.
Effects of Feed Moisture Content, Soybean Ratio and Barrel Temperature on Physical and Functional Properties of Extruded Maize-Soybean Flour Blends
(Tanzania Journal of Science, 2022) Mugabi, Robert; Byakika, Stellah; Muzira Mukisa, Ivan
The effects moisture content, temperature and soybean ratio on expanded product characteristics of extruded maize-soybean blends were studied. Response surface methodology was used to study the effects of extrusion conditions on extrudate properties taking barrel temperature (BT), feed moisture content (FM) and soybean flour ratio (SR) as factors. Expansion ratio (ER), water absorption index (WAI), water solubility index (WSI), hardness and colour (b* - (+) yellowness) of the extrudates were determined. BT and FM had significant effects on ER (p < 0.05). At low FM levels, ER increased with BT. It was observed that both FM and BT significantly affected WAI and WSI. WAI increased as FM increased. Increasing FM to 20% resulted in a decrease in WSI, beyond which an increase was observed. Hardness increased significantly as feed moisture content increased. High SR content significantly increased the extrudate hardness. FM had no significant effect on colour. Colour increased as the SR and BT increased. Significant regression models explained the effects of SR, FM, and BT on all response variables. All of the response variables' R2, were higher than 0.89.
Influence of food safety knowledge, attitudes and practices of processors on microbiological quality of commercially produced traditional fermented cereal beverages, a case of Obushera in Kampala
(Food Control, 2019) Byakika, Stellah; Muzira Mukisa, Ivan; Byenkya Byaruhanga, Yusuf; Male, Denis; Muyanja, Charles
Traditionally, fermented foods were only consumed in regions of their origins but owing to increasing demand, some are finding their way into foreign markets. The challenge though, is the generally uncontrolled nature of the fermentations which raises safety concerns. This paper highlights the food safety challenges associated with traditional fermented foods with a special focus on commercially produced and packaged Obushera, a Ugandan traditional fermented cereal beverage. Microbial counts, titratable acidity (TA) and pH of Obushera samples (n=59) were determined. Food safety knowledge, attitudes and practices (KAP) of processors (n=47) were also evaluated. About 50% of samples did not conform to safety requirements. Obushera had 0.0–7.3 log cfu/mL total and thermo-tolerant coliforms, 0.0–6.2 log cfu/mL E. coli and 0.0–8.1 log cfu/mL Staphylococcus spp. Flour samples had 3.7–7.3 log cfu/g total coliforms, 3.2–7.1 log cfu/g thermo-tolerant coliforms, 1.0–4.9 log cfu/g E. coli and 2.4–7.3 log cfu/g Staphylococcus spp. Salmonella spp was not detected. Obushera (56 out of 59 samples) with pH≤4.0 and TA=0.1–3.1% had coliforms and Staphylococcus spp above the recommended minimum values. Scores showed that processors had fairly good knowledge (63.0 ± 2.3%) and attitudes (52.2 ± 3.0%) but poor practices (38.7 ± 2.4%). There was no correlation between the KAP and product quality. Therefore, processors should adopt better processing technologies that enhance food safety. There is also need for enforcement and regulation of food safety by concerned authorities. Trainings for processors should aim at positively changing their attitudes and causing them to adopt appropriate practices.
Lactic Acid Bacteria Antagonism of Acid-tolerant and Antibiotic-resistant Nonstaphylococcal Pathogenic Species Isolated from a Fermented Cereal Beverage using Baird-Parker Agar
(Journal of agricultural and food chemistry, 2010) Byakika, Stellah; Muzira Mukisa, Ivan; Muyanja, Charles
Fermented foods may contain acid-tolerant and antibiotic-resistant pathogenic microorganisms. Pathogens can be antagonized by lactic acid bacteria, resulting in improved microbiological safety. This study assessed the antagonistic effects of selected lactic acid bacteria against pathogenic bacteria isolated from a cereal fermented food. Materials and Methods: Eight presumptive staphylococci isolated from a commercially produced cereal fermented beverage on Baird-Parker agar supplemented with tellurite were identified using 16S rRNA sequencing. Acid resistance of the isolates was assessed using acidified media (brain heart infusion broth of pH 3.6 and 1.5% acidity) for 48 h followed by taking plate counts. Antibiotic resistance (19 antibiotics) was assessed using the disk diffusion assay. A spot-on-the-lawn method was used to assess antagonistic effects of Lactobacillus plantarum MNC 21, Lactococcus lactis MNC 24, Weissella confusa MNC 20 and Lactobacillus rhamnosus yoba 2012 against Lysinibacillus macroides, Bacillus subtilis, Enterococcus faecalis and Escherichia coli. Results: Presumptive staphylococci were identified as Lysinibacillus macroides (n = 1), Bacillus subtilis (n = 2), Enterococcus faecalis (n = 4) and Escherichia coli (n = 1). These isolates were acid-tolerant (from 6.3 ±0.9 log cfu/mL at 0 h to 3.6 ±0.9 log cfu/mL at 48 h), antibiotic-resistant (multiple antibiotic resistance index of 0.1–0.5) and their growth was inhibited by the lactic acid bacteria (inhibition zone diameters of 14–24 mm). Conclusions: The lactic acid bacteria cultures of MNC 20, MNC 21, MNC 24 and Lactobacillus rhamnosus yoba 2012 can be used in various food fermentations to inhibit growth of bacterial pathogens; thus, improving product safety.
Microbiological safety and physicochemical composition of Bongo, a traditional fermented milk product from Lyantonde district, Uganda
(Scientific African, 2020) Muzira Mukisa, Ivan; Ssendagala, George William; Byakika, Stellah
Traditional fermented dairy products, including Bongo, are an important emerging market owing to their nutritional benefits and probiotic potential. Production of Bongo is unstan- dardized, unregulated and may raise public safety concerns. Microbial counts and physic- ochemical parameters ( n = 30 Bongo samples), production protocol, and hygiene practices of processors ( n = 15) were evaluated. Over 93.3% of the products were contaminated with potentially pathogenic microbes including Enterobacteriaceae, coliforms, Sulphur reducing clostridia, Enterococcus spp. and Staphylococcus spp. About 40% of the samples had pH ≥4.0. Most processors had inadequate hygiene practices which compromised product safety. These results indicate the need for developing product specifications, training processors in good food safety practices and enforcing relevant regulations.
Potential application of lactic acid starters in the reduction of aflatoxin contamination in fermented sorghum-millet beverages
(International Journal of Food Contamination, 2019) Byakika, Stellah; Muzira Mukisa, Ivan; Paul Wacoo, Alex; Kort, Remco; Byenkya Byaruhanga, Yusuf; Muyanja, Charles
Aflatoxin contamination in traditionally fermented cereal-based beverages is a serious food safety challenge considering that commercialization of these products is rising. The challenge is aggravated by the fact that aflatoxin elimination from the food chain is almost impossible. This paper focuses on Obushera, a popular traditional spontaneously fermented sorghum – millet beverage from Uganda. Method: Mold and total aflatoxin levels in cereal flours and Obushera from different markets in Kampala were determined. Ability of lactic acid bacteria (LAB) starters from Obushera; Lb. plantarum MNC 21, W. confusa MNC 20 and L. lactis MNC 24 to bind aflatoxin B1 (AFB1) was evaluated against Lb. rhamnosus yoba 2012 as the reference strain. Results: Mold counts in sorghum, millet and Obushera ranged between 0.0–2.4 log cfu/g, 2.0–6.5 log cfu/g and 2.0–5.5 log cfu/g, respectively. None of the flours complied with food safety standards for molds (maximum = 4 log cfu/g) while 88.0% of Obushera did (standard = maximum 1.3 log cfu/g). Total aflatoxin levels in sorghum, millet and Obushera were 22.3 ± 21.2 ppb, 9.9 ± 10.0 ppb and 10.4 ± 6.1 ppb, respectively. LAB bound 19.3–69.4% of AFB1 in a 1000 ppb solution with binding efficiency in the order of Lb. rhamnosus yoba 2012 = Lb. plantarum MNC 21 > W. confusa MNC 20 = L. lactis MNC 24. The LAB-AFB1complex remained stable under a series of washes with physiological saline. Conclusion: This study indicates that LAB with aflatoxin binding properties can be exploited for controlled cereal fermentations to improve food safety.
Probiotic Enrichment and Reduction of Aflatoxins in a Traditional African Maize-Based Fermented Food
(Nutrients, 2019) Wacoo, Alex Paul; Muzira Mukisa, Ivan; Meeme, Rehema; Byakika, Stellah; Wendiro, Deborah; Sybesma, Wilbert; Kort, Remco
Fermentation of food products can be used for the delivery of probiotic bacteria and means of food detoxification, provided that probiotics are able to grow, and toxins are reduced in raw materials with minimal effects on consumer acceptability. This study evaluated probiotic enrichment and detoxification of kwete, a commonly consumed traditional fermented cereal beverage in Uganda, by the use of starter culture with the probiotic Lactobacillus rhamnosus yoba 2012 and Streptococcus thermophilus C106. Probiotic kwete was produced by fermenting a suspension of ground maize grain at 30 C for a period of 24 h, leading to a decrease of the pH value to 4.0 and increase in titratable acidity of at least 0.2% (w/v). Probiotic kwete was acceptable to the consumers with a score of 6 on a 9-point hedonic scale. The products were stable over a month’s study period with a mean pH of 3.9, titratable acidity of 0.6% (w/v), and Lactobacillus rhamnosus counts >108 cfu g􀀀1. HPLC analysis of aflatoxins of the water-soluble fraction of kwete indicated that fermentation led to an over 1000-fold reduction of aflatoxins B1, B2, G1, and G2 spiked in the raw ingredients. In vitro fluorescence spectroscopy confirmed binding of aflatoxin B1 to Lactobacillus rhamnosus with an efficiency of 83.5%. This study shows that fermentation is a means to enrich with probiotics and reduce widely occurring aflatoxin contamination of maize products that are consumed as staple foods in sub-Saharan Africa.
Probiotic Potential of Lactic Acid Starter Cultures Isolated from a Traditional Fermented Sorghum-Millet Beverage
(International Journal of Microbiology, 2020) Byakika, Stellah; Mukisa, Ivan Muzira; Byenkya Byaruhanga, Yusuf; Muyanja, Charles
)e purpose of this study was to establish the probiotic potential of lactic acid bacteria (LAB) starter cultures, Lb. plantarum MNC 21, L. lactisMNC 24, and W. confusaMNC 20, isolated from a traditionally fermented sorghum-millet beverage from Uganda. )e cultures were examined for tolerance to acid and bile salts, bile salt hydrolase (BSH) activity, antibiotic susceptibility, biogenic amine production, mucin degradation, hydrophobicity, auto-aggregation, adherence to the ileum, coaggregation, and antimicrobial properties against selected pathogenic species. Lb. rhamnosus yoba 2012, a known probiotic, was the reference. )e isolates were tolerant to acid (pH � 3) and bile (1%). W. confusa MNC 20 and Lb. plantarum MNC 21 exhibited medium BSH activity (11–15mm diameter of hydrolysis zone) while L. lactis and Lb. rhamnosus yoba 2012 exhibited low BSH activity (<10mm diameter of hydrolysis zone). All isolates lacked mucolytic activity. Lb. plantarum MNC 21 and W. confusa MNC 20 produced agmatine. )e candidate and reference microorganisms were resistant to 10 of 21 and 5 of 21 antibiotics, respectively. )e isolates exhibited hydrophobic, auto-aggregation and coaggregation properties. )ese three properties were exhibited more (p < 0.05) by the reference than the potential probiotics. )e ability of the potential probiotics to attach onto the goat ileum (7.3–8.0 log cfu/ cm2) was comparable to that of Lb. rhamnosus yoba 2012 (7.6 log cfu/cm2).)efour LAB inhibited E. coli, S. aureus, and S. enterica to the same extent (p < 0.05). )e findings indicated potential probiotic activity of the starter cultures. However, further in vivo examination of these isolates is required to confirm their probiotic capabilities.
A Review of Criteria and Methods for Evaluating the Probiotic Potential of Microorganisms
(Food Reviews International, 2019) Byakika, Stellah; Muzira Mukisa, Ivan; Byenkya Byaruhanga, Yusuf; Muyanja, Charles
Probiotics are live organisms that, when consumed in sufficient quantities, confer health benefits to the host. There is global interest in probiotics research; many are isolated from diverse niches and identified in numerous ways. The challenge is selecting the precise range of tests and methods to use. Some tests are argued to be outdated, biased and/or irrelevant. Screening guidelines exist, but at times are not strictly followed. In many countries, firm regulations regarding probiotics declaration and use are nonexistent. Consequently, some organisms are presented as probiotics without strong scientific evidence. This review discusses common screening approaches, their relevance, strengths and weaknesses. Abbreviations: ADP: Adenosine Diphosphate; ATCC: American Type Culture Collection; ATP: Adenosine Triphosphate; BSH: Bile Salt Hydrolase; Caco-2: Cancer coli-2; cFDA-SE: Carboxyfluorescein diacetate succinimidyl ester; CLSI: Clinical and Laboratory Standards Institute; DNA: Deoxyribonucleic acid; EPN: Epinephrine; FAO: Food and Agriculture Organization; FbPA: Fibronectin binding protein A; FDA: Food and Drug Authority; GIT: Gastrointestinal tract; GRAS: Generally Recognized as Safe; HEPES : 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; HT-29: Human colon adenocarcinoma cells; HT-29 MTX: Methotrexate treated human colon adenocarcinoma cells; ICMR-DBT: Indian Council of Medical Research and Department of Biotechnology; IBS: Irritable Bowel Syndrome; ICR: Inherited Cataract Rat; LAB: Lactic Acid Bacteria; MFI: Mean Fluorescence Intensity; MIC: Minimum Inhibitory Concentration; mRNA: Messenger Ribonucleic Acid; MRS: de Man Rogosa Sharpe; NCCB: Netherlands Culture Collection of Bacteria; OD: Optical Density; PBS: Phosphate Buffered Saline; PGE: Prostaglandin; RBC: Red Blood Cells; SHIME: Simulator of the Human Intestinal Microbial Ecosystem; SDSPAGE: Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis; TLC: Thin-Layer Chromatography; TRAP-6: Thrombin Receptor Activator Peptide-6; WHO: World Health Organization
Sorghum Malt Extract as a Growth Medium for Lactic Acid Bacteria Cultures: A Case of Lactobacillus plantarum MNC 21
(International Journal of Microbiology, 2020) Byakika, Stellah; Muzira Mukisa, Ivan; Byenkya Byaruhanga, Yusuf
Cultivation of lactic acid bacteria cultures is vital for research and commercial production of fermented foods. However, the conventional growth media used are generally costly. Malt extracts from four sorghum varieties (SESO 1, SESO 3, Epuripur, and Eyera) were evaluated as alternative low-cost growth media for Lactobacillus plantarum MNC 21. Saccharified sorghum malt extracts were inoculated with 4 log cfu/mL MNC 21 and incubated at 30°C for 24 h. MRS broth was the reference medium. Microbial counts, pH, titratable acidity (TA), free amino nitrogen (FAN), and total sugars were measured. Maximum microbial counts in the extracts and MRS broth were 9 and 10 log cfu/mL, respectively. Maximum growth rate in the extracts was 0.7–0.9 log cfu/mL/h and 0.8 log cfu/mL/h in MRS broth. (e final pH of the extracts was 3.5–3.6, with an overall increase in TA of 1.2% in Epuripur and 0.2% in other varieties. Final pH and TA of MRS broth were 4.1 and 1.3%, respectively. Total sugars dropped by 95.2% and FAN by 2.1% in MRS broth. In contrast, total sugars and FAN dropped by 5.6–9.1% and 24.9–32.7% respectively, in the extracts. Sorghum malt extracts can be adopted as alternative low-cost growth media for lactic acid bacteria cultures.
Stabilization and Preservation of a Traditional Sorghum-based Fermented Beverage
(Nutrition and Food Sciences Research, 2021) Muzira Mukisa, Ivan; Ahimbisibwe, Stephen; Byakika, Stellah
Traditional fermented cereal beverages such as Obushera from sorghum and/or millet are commercialized owing to their popularity among consumers. However, Obushera separates into two phases after processing, which could be mistaken for spoilage. Additionally, Obushera has a limited shelf life of 4–7 days at room temperature. The objective of this study was to assess the potential of various stabilizers and preservatives for the production of acceptable shelf-stable Obushera. Materials and Methods: Effects of seven treatments of 1) 0.4% xanthan gum, 2) 0.4% carboxymethyl cellulose, 3) Lactobacillus rhamnosus yoba, 4) 0.4% xanthan gum and Lactobacillus rhamnosus yoba, 5) 0.4% carboxymethyl cellulose and Lactobacillus rhamnosus yoba, 6) 0.4% xanthan gum and 0.4% carboxymethyl cellulose and Lactobacillus rhamnosus yoba, and 7) a control (no stabilizers) on sedimentation rate were assessed within 120 h at room temperature. Effects of four treatments of 1) pasteurization (90 C for 10 min) and 0.25% xanthan gum, 2) pasteurization and 0.25% xanthan gum and 0.2% potassium sorbate and 3) pasteurization and 0.25% xanthan gum and 0.1% sodium-benzoate and 4) control (pasteurized with no additives) on shelf stability and consumer acceptability were investigated. Results: Treatments with xanthan (sedimentation index of 0–25%) for stabilizing Obushera were significantly (p < 0.05) more effective than those with no xanthan (sedimentation index of 49–67%). Xanthan (0.25%) significantly (p < 0.05) improved consumer acceptability of Obushera. All preservation treatments (p > 0.05) prolonged the shelf life of the beverage up to four months. No microbial growth was detected in the products during storage while pH (3.7–4.0) and acidity (0.5–0.6%) did not change significantly (p > 0.05). All products were acceptable during storage. Conclusions: Obushera and related products can be stabilized and preserved using xanthan (0.25%) and pasteurization (90 C for 10 min) with no added preservatives.

Browsing by Author "Byakika, Stellah"

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