Influence of immobilization parameters on growth and lactic acid production by Streptococcus thermophilus and Lactobacillus bulgaricus co-immobilized in calcium alginate gel beads

Raw milk was incubated at 7 C for 5 days after it was inoculated with psychrotophic bacteria previously isolated from other raw milks. Then a portion of each sample of milk was pasteurized; the remainder was autoclaved. Streptococcus thermophilus and Lactobacillus bulgaricus were individually inoculated into all pasteurized and autoclaved milks which were then incubated at 37 C and titratable acidity was measured at 2-h intervals. Pasteurized milks precultured with psychrotrophic bacteria supported more acid production than did pasteurized control milks. S. thermophilus and especially L. bulgaricus produced more acid in autoclaved than in pasteurized milks. Cell-free filtrates from cultures of psychrotrophic bacteria were added to raw, pasteurized, and autoclaved milks before they were inoculated with the lactic acid bacteria. Results were similar to those obtained when psychrotrophic bacteria were added to milk. When the cell-free filtrate was added to milks simultaneously with starter cultures, less than 10 h were required to produce conditions in milk favorable for enhanced lactic acid production.

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Lactic Acid Production in Milk Containing Cleaning or Sanitizing Compounds

Journal of Food Protection ◽

10.4315/0362-028x-47.3.197 ◽

1984 ◽

Vol 47 (3) ◽

pp. 197-199 ◽

Cited By ~ 2

Author(s):

MICHAEL B. LIEWEN ◽

ELMER H. MARTH

Keyword(s):

Lactic Acid ◽

Ammonium Chloride ◽

Acid Production ◽

Lactic Acid Production ◽

Streptococcus Thermophilus ◽

Lactobacillus Bulgaricus ◽

Titratable Acid ◽

Streptococcus Lactis ◽

Streptococcus Cremoris ◽

Dry Milk

Sterile reconstituted nonfat dry milk containing 0.1% (v/v) each of 19 cleaning or sanitizing compounds intended for use on dairy farms or in milk factories was inoculated with Streptococcus lactis 4175, Streptococcus cremoris C-13, Streptococcus thermophilus ST4 or Lactobacillus bulgaricus. Milk then was incubated at 32°C for 12 h and pH and titratable acid were determined. Five products (alkaline inflation cleaner, hypochlorite sanitizer-farm use, isopropanol udder wash, ammonium chloride detergent-factory use, alkaline cleaner A-factory use) were inhibitory to at least three of the four lactic acid bacteria at the 0.1% concentration. These were then tested at 0.050, 0.025, 0.012 and 0.006% concentrations. Of the five products, only the isopropanol udder wash (at all four concentrations) inhibited S. lactis and S. cremoris. The isopropanol udder wash at all four concentrations and the ammonium chloride cleaner at 0.050% inhibited L. bulgaricus. S. thermophilus was inhibited by the isopropanol udder wash at 0.050%, whereas the alkaline cleaner A-factory use, at 0.050 and 0.025%, may have been mildly stimulatory to acid production by this bacterium.

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Nitrification and Autotrophic Denitrification in Calcium Alginate Beads

Water Science & Technology ◽

10.2166/wst.1987.0199 ◽

1987 ◽

Vol 19 (1-2) ◽

pp. 175-182 ◽

Cited By ~ 16

Author(s):

Z. Lewandowski ◽

R. Bakke ◽

W. G. Characklis

Keyword(s):

Calcium Carbonate ◽

Calcium Ions ◽

Continuous Flow ◽

Calcium Alginate ◽

Microbial Respiration ◽

Flow System ◽

Alginate Beads ◽

Alginate Gel ◽

Gel Beads ◽

Calcium Alginate Gel

Immobilization of nitrifiers and autotrophic denitrifiers (Thiobacillus denitrificans) within calcium alginate gel was demonstrated. Calcium carbonate reagent was immobilized along with bacteria as the stabilizing agent. Protons released as a result of microbial respiration reacted with calcium carbonate producing calcium ions which internally stabilized the calcium alginate gel. The microbially active gel beads were mechanically stable and active for three months in a continuous flow system without addition of calcium.

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