title: Optimization of the medium for Lactobacillus acidophilus by Plackett-Burman and steepest ascent experiment.
abstract: BACKGROUND
  Lactobacillus acidophilus not only improves the intestinal flora balance but also inhabits the growth of undesirable microorganisms in intestine, which is benefit to the health of humans and animals. Plackett-Burman and steepest ascent experiment are the rapid and concise ways of screening the main effective factors. This study is aimed to select the main influence factors and optimize the medium for Lactobacillus acidophilus by Plackett-Burman experiment and steepest ascent experiment.
  
  
  METHODS
  The ideal carbon source was screened among glucose, maltose, lactose and whey powder, and the ideal nitrogen source was screened among casein hydrolysate, peptone, yeast extract powder, fish meal, carbamide, ammonium sulfate and sodium nitrate by single factor experiment. Plackett-Burman and steepest ascent experiment were applied to screen the main effective factors of Lactobacillus acidophilus among peptone, beef extract, yeast extract powder, glucose, K2HPO4, C6H14O7N2, CH3COONa, MgSO4 and Tween-80. Result. The results indicated that glucose (p = 0.01510) as negative factor and K2HPO4 (p = 0.02017) as positive effect were the significant growth factors of Lactobacillus acidophilus, CH3COONa (p = 0.09273) as positive effect was an important factor, and the optimized medium was as follows: glucose - 21 g/L, K2HPO4 - 3.5 g/L, CH3COONa - 6.5 g/L, peptone - 10 g/L, beef extract - 8 g/L, yeast extract pow.
  
  
  RESULTS
  nd. Lactobacillus acidophilus not only improves the intestinal flora balance but also inhabits the growth of undesirable microorganisms in intestine, which is benefit to the health of humans and animals. Plackett-Burman and steepest ascent experiment are the rapid and concise ways of screening the main effective factors. This study is aimed to select the main influence factors and optimize the medium for Lactobacillus acidophilus by Plackett-Burman experiment and steepest ascent experiment. Material and methods. The ideal carbon source was screened among glucose, maltose, lactose and whey powder, and the ideal nitrogen source was screened among casein hydrolysate, peptone, yeast extract powder, fish meal, carbamide, ammonium sulfate and sodium nitrate by single factor experiment. Plackett-Burman and steepest ascent experiment were applied to screen the main effective factors of Lactobacillus acidophilus among peptone, beef extract, yeast extract powder, glucose, K2HPO4, C6H14O7N2, CH3COONa, MgSO4 and Tween-80. Result. The results indicated that glucose (p = 0.01510) as negative factor and K2HPO4 (p = 0.02017) as positive effect were the significant growth factors of Lactobacillus acidophilus, CH3COONa (p = 0.09273) as positive effect was an important factor, and the optimized medium was as follows: glucose - 21 g/L, K2HPO4 - 3.5 g/L, CH3COONa - 6.5 g/L, peptone - 10 g/L, beef extract - 8 g/L, yeast extract powder - 8 g/L, C6H14O7N2 - 2 g/L, MgSO4 - 0.2 g/L and Tween-80 - 1 mL/L when the maximum viable count could achieve 2.72·109 cfu/mL.
  
  
  CONCLUSIONS
  The experimental model is reliable and the experimental results are of good stability. Variance analysis is performed to determine the adequacy and significance of the linear model. Thus, Plackett-Burman and steepest ascent experiment improve the veracity of optimization the medium for Lactobacillus acidophilus compared with the previous research.
authors.affiliation: College of Life Science and Engineering, Shaanxi University of Science and Technology, China.
authors.forename: He
authors.initials: H
authors.lastname: Chen
authors.affiliation: College of Life Science and Engineering, Shaanxi University of Science and Technology, China.
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Niu
authors.affiliation: Enzyme Engineering Institute, Shaanxi Academy of Sciences, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Qin
authors.affiliation: Enzyme Engineering Institute, Shaanxi Academy of Sciences, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Ma
authors.affiliation: College of Life Science and Engineering, Shaanxi University of Science and Technology, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: College of Life Science and Engineering, Shaanxi University of Science and Technology, China.|Enzyme Engineering Institute, Shaanxi Academy of Sciences, China.
authors.forename: Guowei
authors.initials: G
authors.lastname: Shu
mesh_terms: D000818:Animals; D002417:Cattle; D045424:Complex Mixtures / Q000378:metabolism; D016895:Culture Media, Serum-Free / Q000737:chemistry / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D007202:Indicators and Reagents / Q000378:metabolism*; D007779:Lactobacillus acidophilus / Q000254:growth & development* / Q000378:metabolism; D050296:Microbial Viability; D008954:Models, Biological; D010461:Peptones / Q000378:metabolism; D011136:Polysorbates / Q000378:metabolism; D019936:Probiotics; D015203:Reproducibility of Results; D013501:Surface-Active Agents / Q000378:metabolism; D015003:Yeasts / Q000737:chemistry
chemical_list: D045424:Complex Mixtures; D016895:Culture Media, Serum-Free; D007202:Indicators and Reagents; D010461:Peptones; D011136:Polysorbates; D013501:Surface-Active Agents; D005947:Glucose
keywords: Lactobacillus acidophilus; Plackett-Burman experiment; optimization; steepest ascent experiment