Raffinose Metabolism And Utilisation By L. Plantarum Isolated From Indigenously Fermented Cereal Gruels For Nutritional Improvement

ABSTRACT

Most African foods used in weaning are usually cereal-based gruels fermented by

Lactic Acid Bacteria (LAB). The food mainly supplies carbohydrate; excessive intake of

which might cause malnutrition in growing children. Minimum dietary requirements of a

child could be met through fortification with protein-rich supplements. Soybean is rich in

dietary protein but contains some antinutritional factors and raffinose, an oligosaccharide

responsible for gas formation, bloating and flatulence in weaning children. The use of

microorganisms for hydrolysing raffinose has not been fully exploited in Nigeria. In this

study, the use of LAB to hydrolyse raffinose, reduce antinutritional factors and improve

nutritional composition of such food blends were investigated.

Commercially- hawked “Ogi” (CO) samples, Local Varieties (LV) of sorghum

and maize were obtained from Bodija market, Ibadan and Typed Varieties (TV)-Samsorg

40, Samsorg 41 and Ex-Kano from the Institute of Agricultural Research and Training,

Ibadan. The LAB were isolated from spontaneously-fermenting cereal gruels and

identified using standard methods. Nine strains of Lactobacillus plantarum were selected

based on the abundant production of -galactosidase, and characterized by PCR

amplification of 16SrDNA genes. Plasmid presence was determined using agarose gel

electrophoresis and the effect of plasmid curing was monitored. The growth of the

organisms and metabolites production in different carbon sources were monitored at 200C

to 800C and pH of 3.0 to 9.6. Soyabean was pre-treated by milling, cooking and roasting

while the relationship of the isolates to raffinose metabolism during fermentation was

monitored daily for 5 days. Reducing sugar, residual oligosaccharides, nutritional,

antinutritional factors and alpha-galactosidase were determined using UVspectrophotometer

following Association of Official Analytical Chemist procedures.

Data were analysed using ANOVA at p=0.05.

One hundred and twenty LAB isolates were obtained and identified as L.

plantarum (35.8 %), L. fermentum (12.5 %), L. pentosus (7.5 %), L. acidophilus (15.8

%), L. casei (5.8 %), L. brevis (6.7 %), L. cellobiosus (6.7 %), L. jensenii (5.0 %) and L.

reuterii (4.2 %). Analyses of the nine L. plantarum isolates revealed high sequence

identities (97.0 %). These isolates exhibited significant differences in utilization of

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raffinose at varying concentrations of 0.2 -1.0 mg/mL, while isolates obtained from LV

performed better than those from TV and CO. Fermentation reduced the oligosaccharide

content of the soyabean by 74.6 % while the reducing sugars increased by 65.0 %.

Fortification of the gruel with soyabeans using uncured L. plantarum strains improved

the nutritional quality (protein: 8.4 to 17.8 %, fat: 3.6 to 12.9 %, ash: 2.0 to 3.8 %, Fe: 6.4

to 10.7 mg/100g and Ca: 156.7 to 211.0 mg/100g), and a significant reduction in

antinutritional factors (Tannin: 1.9 to 0.1 mg/g, Phytate: 1.2 to 0.1 mg/g and Trypsin

Inhibitor : 1.2 to 0.0 mg/g) was observed after fermentation . Oligosaccharide content,

reducing sugar, nutritional and antinutritional composition and organoleptic attributes of

the end product were significantly affected by plasmid curing.

Utilisation of raffinose by Lactobacillus plantarum from local food sources reduced

antinutritional factors and oligosaccharides in soybeans. Nutritional quality of cereal

gruels were improved by inclusion of Lactobacillus plantarum.