Sources for isolation of lactic acid bacteria for collection “Lactina”:
- natural sources – fresh milk, whey, plants and herbs, spice plants etc.
- home made yoghurt and other fermented milk products prepared without application of industrial starters
The lactic acid bacterial strains included in “Lactina” collection are isolated and characterized according to the requirements of the international International Dairy Federation (IDF) and International Dairy Foods Assocciation (IDFA) standards and Bergey’s Manual.
“Lactina” collection consists of strains from three groups:
І. group – thermophilic homofermentative lactobacilli
- Lactobacillus delbrueckii ssp. bulgaricus
- Lactobacillus acidophilus
- Lactobacillus helveticus
- Lactobacillus lactis
ІІ. group – thermophilic lactic acid streptococci
- Streptococcus thermophilus
IIІ. group - mesophilic lactococci and lactobacilli
- Lactococcus lactis
- Lactococcus lactis biovar diacetylactis
- Lactococcus cremoris
- Leuconostoc mesenteroides ssp. cremoris
- Lactobacillus casei;
- Lactobacillus plantarum и пр.
Most of the strains from the first two groups were isolated form various natural sources, mainly medicinal plants form ecologically clean high-mountain regions in Bulgaria: Rila, Rhodope, Balkan mountains. Another part was isolated and selected form traditional home made Bulgarian yoghurt form the districts of The Seven Rila Lakes, Skakavitsa, Trun, Pavelsko, etc. At present we continue to isolate and characterize termophilic lactic acid strains Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus in order to diversify and enrich the natural genetic stock of “Lactina” collection. Ongoing identification program includes a variety of modern biochemical and physiological tests. The main criteria and assays applied for estimation of the technological and healthy potential of those bacteria are:
- Growth dynamic in artificial nutrition media
- Acidification potential and dynamic (37-43°C)
- Spectrophotometric determination of the potential for production of D- and L-Lactic acid by means of enzyme tests
- Postacidification activity (5°C and 10°C)
- Organoleptic and texture properties
- Osmotic tolerance
- Antibiotic sensitivity
- Antimicrobial activity
- In vitro tests for survival in gastric and pancreatic juice
- In vitro bile salts resistance
- Flavor and spectrophotometric enzymatic determination of acetaldehyde concentration
- Spectrophotometric enzymatic determination of lactose degradation and release of glucose and galactose
- Biochemical identification tests
- Optimization of bacterial survival during freeze-drying and storage
Traditionally, the cultures for production of Bulgarian yoghurt consist of strains Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus. Many other producers include in addition Lactobacillus acidophilus and/or Lactobacillus lactis. This composition harms the quality, taste and flavor of the end products and results in a worsening and equalizing of the taste of the yoghurt.
The mesophilic lactic acid bacteria form the third group include mainly isolates from raw milk, and home made dairy products from raw milk, sour whey, forages, etc. After characterization, strains of this group were selected for creation of starter cultures for cheese production, according to their acidification potential during the fermentation, flavor, proteolytic and lipolytic activity in the course of the cheese maturation and storage.
In addition, the collection “Lactina” contains Bifidobacteriae isolates belonging to different species (Bifidobacterium bifidum, B. longum, B. infantis, etc.), which are natural inhabitants of the human gastrointestinal tract. Our strains were isolated from small children and are the the basement of biologically active probiotic preparations exported in Russia, Ukraine, Serbia, etc. The strains lactic acid bacteria, appertained to the species Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus helveticus, Lactobacillus lactis, Bifidobacterium bifidum, B. longum, B. infantis, are patented and deposed at National Bank for Industrial Microorganisms and Cell Cultures (NBIMCC), Sofia, Bulgaria.
At present various analyses, clinical trials and in vitro studies are ongoing in order to prove the safety and beneficial health effects of the strains included in Lactina’s probiotic preparations. These studies are being executed at the Medical University of Sofia, Medical University of Pleven, Trakia University, Stara Zagora, Institute of Stock-Breeding Sciences, Kostinbrod, Institute of Organic Chemistry, Bulgarian Academy of Sciences.