ABSTRACT
Aims: The aim of this study was to evaluate the effect of fermented cassava leaves used as diet on provitamin A carotenoid bioefficacy. Study Design: Carotenoid analysis of fermented (F) and non-fermented (NF) cassava leaves, feeding Mongolian gerbils with F and NF leaves and β-carotene bioconversion evaluation. Place and Duration of Study: Felix Houphouet-Boigny University, Abidjan (March to August 2015) and University of Wisconsin-Madison, USA (March to June 2016). Methodology: Fermented cassava leaves were fed to Mongolian gerbils (Meriones unguculatus) and compared with non-fermented leaves and controls. Gerbils (32 days old, n = 46) were vitamin A (VA)-depleted for 3 weeks. After depletion, baseline gerbils (n = 6) were killed and remaining gerbils (n = 40) were weight-matched to 4 groups (n = 10/group) in the following treatments: VA-free feed (VA-); non-fermented leaves (NF); fermented leaves (F); and VA-free feed with daily oral doses of retinyl acetate dissolved in oil (VA+). The feeds were prepared using F and NF leaves at 3.53 and 4.27%, respectively, to equalise daily theoretical VA intake at 35 nmol β-carotene/g feed. Serum and livers were analysed using UPLC®. Results: The daily feed intake from the F and NF groups did not differ (4.38 ± 0.40 g). Serum retinol concentrations did not differ among groups, but the VA+ group had higher liver retinol (1.39 ± 0.32 μmol/liver) than the F and NF groups (P < 0.05). The calculated bioconversion factors were 13 and 37 µg β-carotene equivalents to 1 µg retinol for the F and NF groups, respectively. Conclusion: This study showed that the provitamin A carotenoids from small quantities of F and NF leaves were effective at maintaining VA status of gerbils when assessed by liver stores.
ABSTRACT
Aims: The variability of lactic acid bacteria (LAB) species involved in cocoa bean fermentation would cause inconsistency in the quality of cocoa. The aims of this study is to investigate the physicochemical parameters of cocoa bean fermentation in order to assess the activity and the molecular diversity of LAB involved in cocoa fermentation from six other regions of Côte d’Ivoire. Place and Duration of Study: Laboratory of Biotechnology, UFR Biosciences, University Félix Houphouet-Boigny (Côte d’Ivoire), between October 2016 and September 2017. Methodology: Spontaneous heap fermentations were conducted in six cocoa producing regions during 6 days. Physicochemical analysis of cocoa mass such as temperature, pH, titratable acidity and reducing sugars were carried out. In addition, LAB isolation was performed using plate culture on MRS medium and their fermentative type as well as their profile were determined. In addition, LAB species were determined by restriction profile analysis of the 16S gene. Results: a total of 568 LAB were isolated from cocoa fermentation. Biochemical and morphological identification of these germs revealed the clear dominance of the bacilli form (81.16%) and the heterofermentative type (over 80%) with facultative heterofermentative type recording more than half (54.4%) of the isolated population. Their molecular identification by sequencing the hypervariable zone of the 16S rDNA gene of a few representatives from each restriction group revealed 08 species with a predominance of Lactobacillus plantarum (76.76%) and Leuconostoc mesenteroides (15.31%) associated with minority species. This species diversity could be exploited for selecting appropriate starter cultures. Conclusion: This diversity of LAB species could be responsible for the variability of cocoa quality in Côte d’Ivoire.
ABSTRACT
Aims: This work intends to screen and to identify thermotolerant acetic acid bacteria with acetic acid production capacity at high temperature in cocoa beans fermentation from six cocoa producing regions of Côte d’Ivoire. Study Design: Thermotolerant acetic acid bacteria were isolated from cocoa fermentation. These thermotolerant strains were biochemically characterized and tested for the production of acetic acid in culture medium. Place and Duration of Study: This study was performed in Biotechnology Laboratory, University Félix Houphouët-Boigny (Côte d’Ivoire) from January to November 2017. Methodology: Several strains of acetic acid bacteria were isolated from the traditional cocoa beans heap fermentation process occurred in six major cocoa producing regions of Côte d’Ivoire. These isolates were screened to select thermotolerant strains that were able to produce a good amount of acetic acid. Biochemical identification of thermotolerant acetic acid bacteria was carried out on the basis of biochemical characteristics analysis as acid production from ethanol, oxidation of acetate and lactate, ketogenesis from glycerol or mannitol, formation of water-soluble brown pigment, growth on different carbon sources and acid production from sugars and sugar alcohols. Results: A total of 821 acetic acid bacteria strains were isolated from the cocoa beans heap fermentation of these six regions. Among them, 26 (31.15%) showed growth capacity at 45°C and six (6) grown at 50°C. These 26 strains displayed also acid production capacity at 35°C and at 45°C with acid amount ranged from 1.2 to 24.63 and 0.80 to 1.70 respectively. Biochemical analyses of these thermotolerant strains revealed that the isolates belong to three genera notably Acetobacter, Gluconacetobacter or Gluconobacter. Moreover, all strains were able to grow in medium containing 10% ethanol and to produce acid from various carbohydrates sources. In addition, strain T6HS14 displayed acetoin production capacity while 8 strains were able to produce brown pigment on Yeast extract-Ethanol-Peptone-Glucose medium. Conclusion: This study highlighted the presence of thermotolerant acetic acid bacteria strains involved in Ivorian cocoa fermentation. Furthermore, some isolates displayed a diversity of technological properties which could be used for the improvement of cocoa fermentation process. These predictors, however, need further work to validate reliability.
ABSTRACT
Aims: The breakdown of citric acid contained in the pulp during cocoa fermentation is an important and key property for bacterial growth and for obtaining a well fermented cocoa. The objective of this study was to analyze citrate metabolism in lactic acid bacteria (LAB) isolated from Ivorian fermenting cocoa beans and evaluate their capacity to grow effectively under fermentation conditions. Place and Duration of Study: Laboratory of Biotechnology, UFR Biosciences, University Félix Houphouet-Boigny (Côte d’Ivoire), between August 2014 and April 2015. Methodology: Spontaneous heap fermentations were conducted in three cocoa producing regions during 6 days. Bacteria isolation was performed using plate culture on MRS medium and strains were screened for citrate metabolism using Kempler and McKay medium whereas gas and acetoin productions from citrate were searched. Additionally, the viability of cells under stress conditions related to cocoa fermentation was tested. Results: The results show that a wide rate of LAB strains (75%), mainly heterofermentative possess citrate metabolism, and most of these strains produce gas from citrate but were not able to produce acetoin from citrate. Moreover, some LAB presenting citrate metabolism show a remarkable thermotolerance at 45°C with more than 50% of survival growth rate (SGR), while some exhibited a poor viability (less than 10%) at this temperature. Ethanol at 8-12% was found to have no adverse effect on bacterial growth. In contrast, lactic acid, acetic acid and citric acid exerted individually full inhibition on LAB strains that failed to grow at 0.4% of acid. Conclusion: Taken together, the results indicate that strains studied may preferentially produce lactic acid from citrate and their high proportion should contribute to efficiently break down citric acid during cocoa fermentation. However, occurrence of a high acidity could seriously limit the growth of these valuable potential starter strains in fermentation conditions.