Characterization by MALDI TOF Mass Spectrometry of Yeast and Lactic Acid Bacteria Isolated from ogi and Their Antibacterial Activity
Adesokan Isaac Ayanniran *
Department of Science Laboratory Technology, The Polytechnic, Ibadan and 2Institute of Life Sciences, University of Applied Sciences, (HES-SOValais/Wallis) Western, Switzerland.
Wolfram Manuel Bruck
Institute of Life Sciences, University of Applied Sciences, (HES-SOValais/Wallis) Western, Switzerland.
*Author to whom correspondence should be addressed.
Abstract
Ogi is a Nigerian traditional fermented food commonly produced from maize, millet and/or sorghum. It serves as cheap breakfast meal for low income earners and complimentary meal for infants and convenient for the sick, convalescent and the elderly. It is produced by submerged fermentation and lactic acid bacteria and yeasts have been isolated as responsible for its fermentation. Consumption of ogi has many advantages which include enhanced nutritional value, digestibility, therapeutic benefits and safety against pathogens. Determining the protein profiles of microorganisms using MALDI-TOF (Matrix-assisted laser desorption-ionization time of flight) mass spectrometry are compatible with the results of identification obtained by molecular methods. MALDI-TOF MS are robust, reliable as well as fast and inexpensive to identify Gram-positive bacteria such as LAB and yeast isolates. In this study LAB and yeast isolates were identified using MALDI TOF MS and their antibacterial activity was determined using the agar disc diffusion assay. The 91 LAB isolates identified by the above named method belong to 12 different species. The LAB strain with the highest percentage of occurrence of 59% is Lactiplantibacillus plantarum and it is followed by Limosilactobacillus fermentum which had a percentage of occurrence of 15%. The lowest percentage of occurrence obtained was 1.1% which was recorded for Companilactobacillus pabuli, Enterococcus faecalis, Lactococuss allomyrinae and so on. A total of 43 yeasts were identified and they belong to 5 different species and these are Issatchenkia orientalis (34.9%), Geotrichum candidum (27.9), Pichia occidentalis (32.6), Candida rugosa (1%) and C. tropicalis (1%). The result of antibacterial activity shows that only 26 LAB isolates inhibited at least one of the spoilage and pathogenic organisms employed as indicator. The highest diameter of zone of inhibition (10.8 mm) recorded for L. plantarum OG58 against Escherichia coli while none of the LAB isolates was able to inhibit Bacillus subtilis. The method employed for identification of LAB and yeast isolates from ogi revealed the presence of certain strains which have not been reported before. Also, the LAB strains were able to inhibit the indicator organism tested to varying degree with exception of B. subtilis.
Keywords: MALD-TOF MS, antibacterial activity, lactic acid bacteria, yeast, ogi