Full Length Research Paper

Predominant lactic acid bacteria associated with the traditional malting of sorghum grains

H. Sawadogo-Lingani^1*, B. Diawara¹, R. K. Glover², K. Tano-Debrah³, A. S. Traoré⁴ and M. Jakobsen⁵

¹Département Technologie Alimentaire (DTA) / IRSAT / CNRST, Ouagadougou 03 BP 7047, Burkina Faso.

²Department of Applied Biology, Faculty of Applied Sciences, University for Development Studies P. O. Box 24, Navrongo, Ghana.

³Department of Nutrition and Food Science, University of Ghana, P. O. Box LG134, Legon-Accra, Ghana.

⁴Université de Ouagadougou / UFR – SVT / CRSBAN, Ouagadougou 03 BP 7131, Burkina Faso.

⁵Department of Food Science Food Microbiology, University of Copenhagen, Rolighedsvej 30, 1958 Frederiksberg C Denmark.

*Corresponding author. E-mail: hagretou@yahoo.fr. Tel: 00 226 50 36 37 90 / 00 226 76 63 98 90. Fax: 00 226 50 35 70 29.

Accepted 5 November, 2009

   Abstract

The traditional processes of sorghum grains malting were investigated in Tamale (Northern Ghana) from the raw materials through to the sun-dried malted sorghum including steeping and germination stages. Samples were taken at each processing stage and cultured for the isolation of LAB. The isolates were characterized by basic phenotyping, ITS-PCR / RFLP analysis and identified by partial sequencing of 16S r RNA genes. Their antimicrobial and amylolytic activities and exopolysaccharides production were also investigated. During steeping, the LAB counts in the steep water increased from 10⁵ to 10⁹ - 10¹⁰ cfu/ml and pH of the steep water decreased from 5.08 ± 0.22 to 4.20 ± 0.50. A total of 106 isolates were identified and the predominant isolates belonged to the species Lactobacillus fermentum (58.49%), Pediococcus acidilactici (22.64%), Weissella confusa (11.32%), Enteroccocus faecium, Pediococcus pentosaseus and Lactococcus lactis. Some isolates showed interesting antimicrobial activity (39.62%), slight amylolytic activity (37.73%) and ability to produce exopolysaccharides (90.5%). L. fermentum isolates dominated the microbiota from sorghum grains to malted sorghum. These isolates had technological properties comparable to those responsible for the acidification of sorghum beer (dolo, pito) wort produced from sorghum malt (previously studied), suggesting their potential for use as starter cultures. Suitable isolates of L. fermentum are promising candidates to be used as starter cultures from the initial step of malting, that is, the steeping and are expected to inhibit the growth and survival of pathogens and spoilage microflora, and to control the lactic fermentation of dolo and pito wort or other sorghum malt-based products like infant formulations.

Key words: Sorghum, sorghum malt, lactic acid bacteria, identification, technological properties.