Screening for gum‐producing Lactic acid bacteria in Oil palm ( Elaeis guineensis ) and raphia palm ( Raphia regalis) sap from South‐West Nigeria

摘要

Lactic acid bacteria have wide applications in food processing. Lactic acid bacteria produced exopolysaccharides (EPS) which could be used as possible replacer for commercial stabilizer and thickeners produced by nonfood grade bacteria. Seventy‐two samples of Oil and Raphia palm sap were collected in eighteen locations across South‐Western Nigeria and screened for exopolysaccharide production in 6% sucrose agar using streaked plate method. Four hundred EPS‐producing bacteria (EPB) isolated were clustered based on morphological characteristics into two broad groups and preliminary screened for EPS‐producing capacity. Twenty representative of EPB were selected from the broad groups for tentative identification by API 50CHL and 10 high yielding EPB were selected for large‐scale EPS production. Each strain was inoculated into 6% sucrose broth with 3% (v/v) preculture grown overnight in a 1.5?ml flask and incubated at 37°C for 72?hr. The EPSs were purified and freeze‐dried prior to quantification of yields. EPS‐producing bacteria were identified as Leuconostoc lactis , Lactobacillus fermentum , Lactobacillus delbrueckii ssp. lactis , L.?delbrueckii ssp. delbrueckii , Lactobacillus acidophilus , Lactobacillus plantarum, Lactobacillus crispatus, and Leuconostoc mesenteroides ssp. mesenteroides/dextranicum . EPS yield ranged from 132–810.75?mg/L and EPS‐producing potential of lactic acid bacteria (LAB) strains ranged; 36% (132–245?mg/L), 36% (250–460?mg/L), and 28% (461–820?mg/L). L.?plantarum had the highest EPS yield of 810.75?mg/L whereas L.?crispatus had the least yield 242.5?mg/L. These results suggest that majority of LAB in palm wine saps are gum‐producing bacteria. Leuconostoc and Lactobacillu s were the most abundant LAB found in this study while L.?plantarum could have applications as potential starter cultures for the production of exopolysaccharides (EPS) at industrial level.