Enzymatic Activity of Lactobacillus Grown in a Sweet Potato Base Medium

Aim: To study the impact of sweet potatoes on α-glucosidase, β-glucosidase, acid phosphatase, and phytase activity of Lactobacillus.

Study Design: Enzymatic activity of seven strains of Lactobacillus grown in a sweet potato medium (SPM) was determined and compared to the standard lactobacilli MRS. Strains having the highest enzymatic activity were further enhanced by metal ions.

Place and Duration of Study: Food Microbiology and Biotechnology Laboratory, North Carolina A&T State University, Greensboro, NC, USA, between September 2012 and May 2013.

Methodology: Lactobacillus strains were grown in SPM and MRS at 37ºC for 16 h. At the end of incubation, bacterial population (log CFU/mL) was determined by plating and enzymatic activity was determined spectrophotometrically using the corresponding substrate.

Results: Lactobacillus strains continue to grow in SPM and MRS and reached averages of 10.98±0.49 and 10.92±0.55 log CFU/mL respectively. Growth of Lactobacillus strains in SPM led to higher β-glucosidase, acid phosphatase, and phytase activity than MRS. Strains of L. reuteri (CF2-7F and SD2112) grown in SPM showed the highest acid phosphatase (15.84±1.05 and 20.56±1.49 Ph U/mL), and phytase (0.66±0.14 and 0.65±0.11 Ph U/mL) respectively. The highest β-glucosidase (36.04±3.16 Glu U/mL) activity was obtained from L. delbrueckii subsp. bulgaricus SR35 grown in SPM. In addition, acid phosphatase and phytase produced by L. reuteri CF2-7F growing in SPM were further increased by the addition of Mn2+ (70.1 and 41.8%) or Mg2+ (94.7 and 20.9%) respectively. β-glucosidase activity of L. reuteri was increased in a range of 4.1 to 130.6% due to the addition of metal ions.

Conclusion: Components in sweet potatoes could increase enzymatic activity of Lactobacillus and the addition of metal ions could further produce an enhanced level of these enzymes.