Jean Justin Essia Ngang

Background: This study aimed to improve the cassava retting efficiency of starter Sta_96, a fermented cassava flour obtained after four days of fermentation, by incorporating bacteria of the genus Streptomyces. Methods: Streptomyces isolates were obtained from Sta_96, farm soils, and a cassava peel dump. The subsequent pectinolytic and cellulolytic activities, along with the associated ability to soften cassava roots, were evaluated. The most effective isolates were incorporated into Sta_96 at a concentration of 106 CFU/g, and the associated retting and detoxification efficiencies were assessed. Results: Of the 33 Streptomyces isolates recovered, 24 produced pectinases, with hydrolysis halos ranging from 11.0 ± 1.4 mm to 42.5 ± 3.5 mm. Sixteen of these displayed cellulase activity, with halos ranging from 16.0 ± 0.1 mm to 40.0 ± 0.1 mm. STF 16 showed the highest softening efficiency, achieving a retting time of 38.6 ± 0.4 h, and significantly improved the performance of Sta_96 by reducing the retting duration from 44.5 ± 0.6 h to 24.3 ± 0.4 h, representing a 45.39% reduction. STF 16 also demonstrated substantial detoxification efficiency (~85%). Conclusions: This is the first report demonstrating that Streptomyces species can act as efficient cassava retting agents. Incorporation of STF 16 into the Sta_96 starter markedly accelerated root softening to about 24 hours while ensuring complete elimination of cyanide. This approach represents a promising strategy for improving fermentation efficiency and product safety in cassava-processing industries.

Aims: Evaluate the effect of cassava cell wall neutral sugars and uronic acids on the ability of cassava to be retted by a traditional starter (sta_96). Place and Duration of Study: Sample: collected from a farm in the Center region in Cameroon. All the analysis were performed at the Department of Microbiology of the University of Yaounde 1 in Cameroon, between June 2024 and December 2024. Methodology: height (08) different local cassava varieties 12 months aged were submitted to fermentation with Sta_96 and their retting kinetic parameters (retting rate and retting times) were assessed by penetrometry. Furthermore, their parietal compounds (neutral sugars and uronic acids) and non-parietal compounds (reducing and total sugars) were analyzed by spectrophotometry and the data obtained were submitted to correlation analysis. Results: It was observed that the roots of the VB 3, CB 1, CB 2, sweet, 6M, and CR varieties softened more easily, with fermentation rates ranging from 1.04 ± 0.88 to 1.75 ± 0.23 cm/h and retting times ranging from 42.64 ± 7.07 to 50.64 ± 0.44 h. The roots of the VB 1 and VB 4 varieties softened with greater difficulty. Negative correlations (-0.79 and -0.881 respectively for neutral sugars and uronic acids) were observed between neutral sugars, uronic acids and softening rate, suggesting that these compounds increase cassava’s retting time by decreasing it fermentation rate. This study shows that the cassava’s softening ability is linked to the neutral sugars and uronic acids content in cassava root walls. Conclusion: Taking into account the cell wall composition in the formulation of starters can lead to a standardization of the cassava roots retting time.

Cocoa beans are often obtained from exposed fermentation and hence may carry many microbial hazards in the production of cocoa‐derived products. The aim of this work was to assess the microbial quality along the production chain of cocoa mass and the effect of mild heat (ambient temperature, 50°C, 55°C, 60°C and 65°C) and cold storage (refrigeration and freezing) of the latter on deliberately inoculated Klebsiella oxytoca , Escherichia coli , Saccharomyces cerevisiae and Aspergillus brasiliensis survival. It was observed that steam pasteurisation and cocoa roasting can reduce the level of cocoa bean mould from 4.82 Log CFU/g to nondetected levels and total bacteria counts from 6.63 Log CFU/g to 1.94 Log CFU/g in cocoa nibs. The refining process was a critical contamination stage as it contributed to increased microbial contamination. Regarding the challenge testing with the four strains, the deactivation potential of the different cocoa mass treatments was directly proportional to the increase in temperature. In general, the order of sensitivity to cocoa mass treatments was Klebsiella oxytoca , Saccharomyces cerevisiae , Escherichia coli and Aspergillus brasiliensis. The results obtained in this work will contribute in providing new approaches to food safety assurance in the cocoa industry, in particular during the production of cocoa mass.

This study investigated the fungal distribution on maize across Nigeria′s diverse agroecological zones. A total of 270 maize samples were collected from farms (90), markets (90), and storage facilities (90) from all seven agroecological zones in the country. The fungal strains were identified at the species level using conventional identification techniques, molecular methods, and phylogenetic analysis. The results showed that the highest fungal loads were recorded in the Sahel savanna (SHS), Sudan savanna (SS), and northern Guinea savanna (NGS) zones, with NGS showing peaks above 4.0 × 10 ⁶ CFU/g, particularly in farm and store samples. Lower fungal loads were observed in the mid altitude, derived savanna (DS), and humid forest (HF) zones, with median values mostly below 5.0 × 10 ⁵ CFU/g. Notably, the variability and presence of outliers were more pronounced in the SHS, SS, and NGS zones, indicating inconsistent contamination levels. A total of 986 fungal isolates were obtained from across the different agroecological zones. The fungi strains were grouped into 10 fungal genera, namely, Aspergillus sp. (42. 87%), Fusarium sp. (33.50%), Penicillium sp. (18.32%), Rhizopus sp. (3.46%), Absidia sp. (0.5%), Mucor sp. (0.5%), Curvularia sp. (0.3%), Microsporum sp. (0.1%), Alternaria sp. (0.1%), and Cladosporium sp. (0.1%). The molecular‐based identification of some of the isolates revealed the presence of new species in the crop, Talaromyces sayulitensis , Aspergillus montevidensis , Epicoccum sorghinum , Aspergillus piperis , Exserohilum rostratum , and Tyrophagus putrescentiae . The studies demonstrated a high prevalence of mycotoxin‐producing fungi, particularly from the genera Aspergillus , Fusarium , and Penicillium , which pose serious health risks due to their potential to contaminate food supplies with harmful toxins like aflatoxins and fumonisins.

The poultry industry produces an average of 9 million tonnes of keratinous waste per year. This waste is rich in essential amino acids and is an important ingredient in the manufacture of more balanced animal feeds. However, access to keratin amino acids that are difficult to hydrolyse by conventional proteases such as papain, pepsin and trypsin means that we have to use physico-chemical methods that consume a lot of energy and, what's more, destroy these essential amino acids. Furthermore, livestock feed contains pathogenic micro-organisms whose inhibition by the abusive use of synthetic antibiotics is leading to the emergence of antibiotic resistance. The aim of this study was to isolate keratinolytic Actinomyces sp. capable of inhibiting the growth of pathogenic bacteria commonly found in animal feed. Soil samples from keratin waste dumps were used as a matrix for the isolation of Actinomyces sp. These were then inoculated onto solid and liquid media enriched with keratin in order to screen and compare their keratinolytic activity. Finally, the antagonism of the best keratolytic isolates to Escherichia coli, Salmonella enteritidis and Staphylococcus aureus was assessed. The study shows that 19 of the 22 actinobacteria isolated produced keratinase hydrolysis diameters ranging from 9.5±3.5mm to 15.5±0.7mm. Seven isolates were able to inhibit the growth of the three pathogenic strains and isolate KER-2 was the most active isolate with inhibition diameters ranging from 15.8±4.6mm to 22.5±0.7mm. This work shows the potential of soil-isolated bacteria to convert bird feather waste into a potential pathogen-free animal feed.

Aims: Evaluate the effect of cassava cell wall neutral sugars and uronic acids on the ability of cassava to be retted by a traditional starter (sta_96). Place and Duration of Study: Sample: collected from a farm in the Center region in Cameroon. All the analysis were performed at the

In this study, a risk assessment on Vibrio parahaemolyticus infections was carried out in order to estimate the likelihood of gastroenteritis for Cameroonians after consumption of roasted shrimp (Penaeus monodon). The Codex Alimentarius Commission framework was used in this study. Based on the distribution of total V. parahaemolyticus in shrimp and literature information indicating that nonhaemolysing carrier strains could be pathogenic to humans, the cooking, and consumption patterns, the daily exposure level generated in this study, and the dose-response model from other studies, the infectious risk was evaluated and quantified by the Monte Carlo simulation. This simulation was realized based on 10,000 iterations using the Model Risk software, version 4.0, in combination with Microsoft Excel. To better quantify the exposure of consumers and the resulting risk of infection, several scenarios reflecting the minimal, average, and maximal exposures were undertaken. According to the results, the 90 confidence intervals for minimum and maximum exposures ranged from 15 to 24 colony-forming units per day (cells/day) and from 160 to 228 cells/day, respectively. Based on the modal scenario, 90 of the population consuming this shrimp is exposed to V. parahaemolyticus loads ranging from 74 to 110 cells/day, indicating a risk of infection ranging from 1.2 to 1.8 cases per million of consumption. The estimated number of annual disease cases based on annual production is between 1 and 10 cases. This reflects a relatively low risk of infection for roasted shrimp. Good hygiene practices during handling, cooking, and storage may help reduce the actual risk.

Aim: the aim of this study was to determine sensory profile, through the use of just-about-right (JAR) scales and penalty analysis, of Bobolo and Chikwangue from the cassava roots fermented with previously cassava-fermented chips powder (PCFCP). Furthermore, retting time, cyanide content and pasting properties of retted roots were evaluated. Methods: for that, two samples of Bobolo and Chikwangue obtained from two cassava retting methods were studied: a control made from the retting without PCFCP and a product made from retting with PCFCP. Results: retting time was carried out in 48 hours less with PCFCP and 60% of cyanide reduction more than control. No major modifications occurs in pasting properties of paste fermented with PCFCP. The sensory analysis indicated high levels of acceptability for products made from retting with PCFCP. The penalty analysis showed that attributes “too sour” and “too much fermented odor” affected the acceptability of the Bobolo from retting without PCFCP significantly. Conclusion: fermentation of cassava through the use of PCFCP is suitable to improvement of sensory characteristics of fermented cassava by-products.

Aims: To compare the physicochemical (water, total titratable acid, amylose and amylopectin contents), functional (swelling and solubility powers) and pasting characteristics of cassava flour retted in two different ways. Study Design: Flours were produced from two cassava cultivars subjected to natural and accelerated fermentations using a multi-strain mixed starter. Place and Duration of Study: Department of Microbiology of the University of Yaounde 1 and Department of Food Science and Nutrition at the University of Ngaoundere, both in Cameroon, between November 2019 and February 2020. Methodology: The cassava roots of each cultivars were divided into two groups and fermented by submerging peeled roots in tap water. One group of each cassava cultivar was inoculated with 1% (w/w) of the starter, while the other was subjected to a spontaneous fermentation. Retting stopped after the softening of the roots; that is after twenty-six hours for the inoculated groups, and after seventy-two hour for the control groups. The fermented roots were then squeezed, dried and grounded in a blender. Flours obtained were subjected to physicochemical, functional and pasting analysis. Results: Flours produced in accelerated fermentation (AF) were characterized by their low amylopectin contents (46.59% and 43.57%), swelling power (6.71% and 7.56%), solubility (6.03% and 7.96%), and peak viscosity (6182 cP and 5676 cP) for Six-mois and Mintol-meko flours respectively. Whereas setback viscosity (1032 cP and 1068 cP), stability (0.27 and 0.24) and final viscosity (3565 cP and 3566 cP) of flours from natural fermentation (NF) were lower than those from AF. Conclusion: The accelerated fermentation reduces the tendency of paste to downgrade, that is responsible for staling in baked products and could therefore produce flours that are less fluid.