Lactis Biovar Research Articles

Effect of freezing temperature on rate of survival of lactococcus cultures during lyophilization

The important component in the activities of the collection of starter microorganisms is the preservation of the pool of the strains valuable for industrial production. Lyophilization (also known as freeze drying) is a widely used method for the long-term storage of the collection cultures. The critical parameter of the process of lyophilization is the pre-freezing temperature. This article brings forward the results of researches of the rate of survival of lactococcus strain cultures during their lyophilization with pre-freezing at the temperatures of minus 20 °C, minus 30 °C and minus 55 °C. Reconstituted 10% skim milk was used as the medium for strain culturing and lyophilization. Different reactions were detected among the microorganisms of Lactococcus lactis subsp. lactis, Lactococcus cremoris and Lactococcus lactis subsp. lactis biovar. diacetylactis for their freezing and lyophilization under the tested conditions. The highest rate of survival of lactococcus strains was observed at the freezing temperature of minus 20 °C. The most resistant cultures appeared to be Lactococcus lactis subsp. lactis biovar. diacetylactis — their rate of survival after lyophilization at minus 20 °C amounted to 42.6-57.9%. The lowest survival rate was recorded for Lactococcus cremoris in all freezing modes (from 3.1 to 15.7%). Lyophilization of lactococcus collection cultures ensures high survival rate of the cells.

Formation of cheese pattern when using monospecies cultures

The article presents the results of a study of the influence of monospecies gas-aroma-forming cultures Lactococcus lactis subsp. lactis biovar. diacetylactis (L. diacetylactis) and Leuconostoc subsp. on the peculiarities of pattern formation in cheeses with a low second heating temperature molded from a layer. The studied cultures were used at a dose of 0.6% of the total milk volume as as single starter microflora in the model cheeses (1-M and 2-M) and additional microflora along with the main lactococcal microflora (Lactococcus lactis subsp. lactis; Lactococcus cremoris) in the control cheeses (1-K and 2-K). The model and control cheeses were subjected to microbiological tests (total number of lactic acid microorganisms, number of L. diacetylactis and Leuconostoc subsp.), physicochemical (mass fraction of moisture, pH), biochemical (mass fraction of lactose) and organoleptic studies after pressing and during ripening at the age of 15, 30, 45, 60 days. It has been established that the use of a culture of citrate-fermenting lactococci L. diacetylactis ensures a stable lactic acid fermentation process during the production and ripening of the model and control cheeses, the formation of an elastic consistency and the desired pattern with eyes of a regular round shape. The use of the hetero-fermentative culture Leuconostoc subsp., as single starter microflora, does not guarantee the required level of lactic acid fermentation during cheese production and leads to an increase in the moisture content of the cheese mass after pressing and overacidification of the cheese in the first stages of ripening, which together contributes to the formation of an overly plastic consistency and an overdeveloped pattern in the form of cracks. The use of Leuconostoc subsp. as a gas-aroma-forming component of a traditional starter culture for semi-hard cheeses, also consisting of mesophilic lactococci Lc. lactis subsp. lactis and Lc. cremoris, causes the development of a nest-like pattern, which does not fully ensure the formation of the desired pattern with regular rounded eyes.

The aroma profile of butter produced using different starter cultures

The aroma of fermented dairy products is greatly influenced by starter cultures and by the lactic acid bacteria strains that are used as starter cultures. Experimental butter samples were produced using no starter culture, by a commercial starter culture (Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis biovar. diacetylactis, Leuconostoc mesenteroides), by a prepared bacteria mix (Lactococcus lactis subsp. lactis EM1, Lactococcus lactis subsp. cremoris EM28, Lactococcus lactis subsp. lactis biovar. diacetylactis G49, Leuconostoc mesenteroides B3), and by a prepared bacteria mix fortified with Lactobacillus rhamnosus B19 (L. rhamnosus B19). The aroma profile of the butter samples was investigated using a gas chromatography mass spectometry method (GC-MS). A total of 92 components were determined in the butter samples, including acids (12), alcohols (20), aldehydes (9), alkanes (6), esters (8), ketones (19) and several other aroma compounds (18). The sample containing the prepared starter culture had the most detectable aroma components, while the lowest number of aromatic components were found in the sample without a starter culture. 2,3-butanedione (diacetyl) was not detected in the sample without a starter culture. 2-Butanone 3-hydroxy- (acetoin) content was the highest in the sample containing the commercial starter culture and the lowest in the sample without a starter culture.

Development of kefir technology with celery pure

The creation of new types of functional food products is an actual direction of the development of the food industry at the present time. The purpose of the work was to develop the technology, to investigate the properties and quality indicators of kefir using celery puree. Experimental studies of organoleptic, physicochemical and microbiological indicators of kefir were conducted in the laboratory of the department of technology of milk and dairy products. For the production of kefir we used a fermentation culture directly applied by DVS company “CHR Hansen” (Denmark) Kefir-1, which includes Debaryomyces hansenii yeast and meso- and thermophilic lactococci: Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis biovar. diacetylactis, Lactococcus lactis subsp. lactis, Leuconostoc, Streptococcus thermophilus. Stalks of celery were used to prepare puree in laboratory conditions. Stalks celery were washed, cut into small cubes. Chopped celery cubes were placed in a vessel, a small amount of water was added, brought to a boil. After that, the water was drained, and the celery cubes were carefully ground with a blender to a smooth puree-like consistency. At the first stage, kefir recipes were developed using different amounts of celery puree. We produced 3 samples of kefir: sample 1 – use of celery puree in the amount of 20 % to the weight of the normalized mixture; sample 2 – 30 %; sample 3 – 35 %. Kefir was made by the tank method. The cooled milk was sent for normalization. After normalization, the milk mixture was sent for pasteurization at a temperature of (95 ± 1) °C with a holding time of 5 minutes. Fermentation culture Kefir-1 was added to the milk mixture cooled to a temperature of (30 ± 1) ºС. To evenly distribute the culture, mixing was used for 10-15 minutes. The mixture was subjected to fermentation at a temperature of (30 ± 1) ºС. After fermentation, celery puree was added to the milk mixture in the amount of 20, 30 and 35 % to the product weight. The mixture was thoroughly mixed and the product was immediately cooled to a temperature of 8 °C and sent to maturation for 12 hours. Organoleptic, physical and chemical and microbiological indicators were studied in the finished product in accordance with DSTU 4417:2005 “Kefir. Specifications”. The titrated acidity was determined according to GOST 3624-92 “Milk and dairy products. Titrometric methods of determining acidity”. Active acidity was measured using an electronic pH meter “Muttler Toledo MP220”. The total number of lactic acid cultures was determined by parallel inoculation of dilutions of yogurt samples in Petri dishes on Lactobacagar medium followed by incubation in a thermostat at a temperature of (37 ± 1) ºС for 3 days under anaerobic conditions. According to organoleptic parameters, in particular, better appearance and consistency, it is recommended to use celery puree in the amount of 35 % of the product weight in kefir technology. The physical and chemical parameters of the milk-vegetable product after maturation are as follows: titrated acidity 75–80 ºT, active acidity 4.8–4.7 units pH, mass fraction of fat 2.5 %. During storage for 14 days, acidity changed the least in milk-vegetable kefir with celery puree in a sample with 35 % puree, which is caused, in our opinion, by the presence of essential oils in celery puree, which suppress the development of lactic acid microflora. The results of determining the number of viable lactic acid bacteria in kefir during storage at a temperature of (4 ± 2) ºС for 14 days indicate the intensification of the growth of lactic acid bacteria. Their development was more active in the sample using the smallest amount of celery puree.

Identification of a Prophage-encoded Abortive Infection System in Levilactobacillus brevis

Abortive infection systems (Abi) are phage resistance systems that can be prophage-encoded. Here, two genes encoding an Abi system were identified on a prophage sequence contained by the chromosome of the Levilactobacillus brevis strain UCCLBBS124. This Abi system is similar to the two-component AbiL system encoded by Lactococcus lactis biovar. diacetylactis LD10-1. The UCCLBBS124 prophage-derived Abi system (designated here as AbiL124) was shown to exhibit specific activity against phages infecting L. brevis and L. lactis strains. Expression of the AbiL124 system was shown to cause reduction in the efficiency of plaquing and cell lysis delay for phages of both species.

Effects of starter culture and storage on volatile profiles and sensory characteristics of yogurt or cream butter

In this study volatile compounds and sensory properties of butter produced from cream or yogurt using Lactococcus lactis subsp. lactis biovar. diacetylactis or Leuconostoc mesenteroides subsp. cremoris as well as a mixture of these two bacteria were investigated over 60 days. A total of 10 esters, 6 aldehydes, 11 ketones, 16 alcohols, 6 acids, 2 sulphides, 3 terpenes, and 3 miscellaneous compounds were detected. There were more volatile compounds in cream butter than in yogurt butter. While S-methyl thioacetate was only found in yogurt butter samples, hexanal, ethanol, 2-nonanone, 2-pentanone, 2-heptanone, acetic, butanoic (butyric) and hexanoic acid were the most abundant volatiles in both cream and yogurt butter. The results showed that the use of starter in the manufacturing of yogurt butter, which is traditionally produced without starters, affected the volatile compounds and sensory properties. The highest general acceptability scores were given to the butter samples containing mixed cultures at the end of storage.

Diversity in NaCl tolerance of Lactococcus lactis strains from dl-starter cultures for production of semi-hard cheeses

Mesophilic starter cultures, such as Lactococcus lactis, are exposed to NaCl stress during brining of cheeses influencing their viability. We investigated the effect of NaCl water solutions, used at concentrations of 3.4%, 8.0% and 15% (w/v), on viability of Lc. lactis subsp. cremoris, Lc. lactis subsp. lactis biovar. diacetylactis and Lc. lactis subsp. lactis isolated from commercial dl-starter cultures. Viability was assessed by plate counts and flow cytometry. Bacterial viability decreased with increased concentration of NaCl in a strain-dependent manner (between 0.02% and 62% cfu at 15% (w/v) NaCl, compared with controls at 0.85% (w/v) NaCl), whereas no significant differences were detected between the subspecies. Viability levels determined by plate counts were generally lower than by flow cytometry, indicating the presence of viable but not culturable cells. Knowledge of salt tolerance of Lc. lactis strains would enable rational selection of starter cultures targeting production of cheeses with different NaCl content.

Detection of enzymes produced by lactic acid bacteria isolated from traditionally made Serbian cheese and their role in the formation of its specific flavor

Nine species (sixteen isolates) of lactic acid bacteria (LAB) isolated from traditionally made Serbian cheese were evaluated for their enzymatic activities in order to select indigenous strains of technical interest for the manufacture of cheese. These strains were selected based on their previously determined biochemical and physiological characteristics, as well as their antimicrobial activity, and were identified as Lactococcus lactis subsp. lactis (one isolate), Lc. lactis subsp. lactis biovar. diacetylactis (five isolates), Lactobacillus fermentum (two isolates), Lb. plantarum (one isolate), Lb. brevis (one isolate), Enterococcus faecalis (three isolates), E. faecium (one isolate), E. durans (one isolate) and E. hirae (one isolate). The enzymatic activities (acid and alkaline invertases, alkaline phosphatase, alkaline protease, a-amylase) were measured by using the spectrophotometric method. The results indicated that all Lactobacillus isolates showed protease, amylase, and alkaline phosphatase activities, while the activities of acid and alkaline invertases were not observed. The Lactococcus isolates showed protease, acid invertase and alkaline phosphatase activities, except the KGPMF50 isolate, which showed no alkaline phosphatase activity. The tested Enterococcus isolates showed weakly and strain-specific enzymatic activity. The results indicated that the enzymes produced by the investigated strains have a role in the formation of the specific flavor of cheese and that these isolates, especially Lactobacillus isolates, showed the potential for use in the dairy industry or applied biotechnology.

Tolerancija autohtonih bakterija mlečne kiseline na različite uslove prerade in vitro

In this paper, the effect of different temperatures, pH, and NaCl concentration on the growth of autochthonous lactic acid bacteria isolated from traditionally made Serbian cheese (Sokobanja area) was investigated by using the spectrophotometric method. Growth of tested Lactobacillus (Lb. fermentum, Lb. plantarum, and Lb. brevis) and Lactococcus lactis subsp. lactis biovar. diacetylactis five isolates were better in acidic pH, while the growth of Enterococcus isolates (E. durans, E. faecium, and E. faecalis) was better in basic pH, at 37 °C. At 4 °C after 24 h, none of the tested bacteria showed growth. Since the autochthonous isolates were tolerant to a tested range of dairy processing conditions, further studies need to include the characterization of enzymatic activity of selected isolates, as well as the ability to use these isolates like starter cultures or food supplements in dairy or non-dairy products.

Functional dairy product

A functional orientation fermented milk product on a direct starter with the apple powder addition was obtained. The apple pomace powder obtained under gentle conditions enriches the kefir product with pectin substances, vitamins E, B2, B6, iron and potassium. The apple pomace powder was obtained in a vibration vacuum dryer - a mill, which provides drying under vacuum with the combination of grinding processes and intensive vibrational action. This technology allows obtaining a fine powder with a moisture content of 4–6%, minimizing the raw material valuable components loss during drying, since the process temperature is no higher than 40o C. The starter consists of thermophilic, mesophilic lactic acid Streptococcus,and Lactobacillus acidophilus (Lасtococcus lactis sp lactis, Laсtococcus lactis sp. cremoris, Laсtococcus lactis sp. lactis biovar. diacetylactis, Saccharomyces unisporus, Streptococcus salivarius sp. thermophiles). The nutritional value of kefir product with the functional powder introduction was calculated. An approbation of the proposed K-10,12 starter for the preparation of kefir product with the apple powder addition and the analysis of consumer properties in comparison with traditional kefir were carried out. Each starter batch was analyzed for the absence of extraneous microflora, by microscopic examination and the presence of gas-forming microflora. Quality control indicators of enriched kefir product was being conducted during the entire shelf life. Organoleptic and physico-chemical quality assessment of the finished dairy product was performed on a 10-point scale. The control of microbiological indicators of kefir product was carried out in comparison with traditional kefir, obtained with the use of ordinary kefir fungi. The use of direct starter for kefir production solves many technological problems and makes its manufacture in small enterprises possible.

Molecular, physiological and phylogenetic traits of Lactococcus 936-type phages from distinct dairy environments

Bacteriophage infection of Lactococcus species can cause serious disruption of dairy fermentation processes. The most common isolates from the dairy environment are Siphoviridae lytic 936-type phages. To gain specific knowledge about this group of phages in Polish dairies, we examined 90 isolates from 8 different locations. Based on restriction fragment length polymorphism analysis, coupled with physiological and molecular studies, the isolated phages were divided into 8 distinct groups. Whole-genome sequencing of single representatives from each phage group provided data about their biology and genetic composition. The phages present an overall conserved genome organization. High sequence homology to another Polish isolate, Lactococcus phage bIBB29, indicates their close phylogenetic relatedness to this strain. Such similarity may be suggestive of a general genome conservation among phages persisting in Polish dairies. Comparative genome analyses with other 936-type phages revealed several discriminative traits, including the presence and position of HNH endonuclease genes, varying number of orfs in the early gene region, and a putative TpeX gene. Interestingly, host range of the sequenced phages was restricted to L. lactis subsp. lactis biovar. diacetylactis strains. The results provide new data regarding phages present in the Polish dairy environment and permit analysis of their biology, genome composition and relatedness to other Lactococcus 936-type phages.

Genetic and phenotypic features defining industrial relevant Lactococcus lactis, L. cremoris and L. lactis biovar. diacetylactis strains

Lactococcus lactis strains constitute one of the most important starter cultures for cheese production. In this study, a genome-wide analysis was performed including 68 available genomes of L. lactis group strains showing the existence of two species (L. lactis and L. cremoris) and two biovars (L. lactis biovar. diacetylactis and L. cremoris biovar. lactis). The proposed classification scheme revealed coherency among phenotypic (through in silico and in vivo bacterial function profiling), phylogenomic (through maximum likelihood trees) and genomic (using overall genome sequence-based parameters) approaches. Strain biodiversity for the industrial biovar. diacetylactis was also analyzed, finding they are formed by at least three variants with the CC1 clonal complex as the only one distributed worldwide. These findings and methodologies will help improve the selection of L. lactis group strains for industrial use as well as facilitate the interpretation of previous or future research studies on this diverse group of bacteria.

Lactic Acid Bacteria from Kefir Increase Cytotoxicity of Natural Killer Cells to Tumor Cells.

The Japanese fermented beverage, homemade kefir, contains six lactic acid bacteria: Lactococcus. lactis subsp. Lactis, Lactococcus. lactis subsp. Cremoris, Lactococcus. Lactis subsp. Lactis biovar diacetylactis, Lactobacillus plantarum, Leuconostoc meseuteroides subsp. Cremoris and Lactobacillus casei. In this study, we found that a mixture of the six lactic acid bacteria from kefir increased the cytotoxicity of human natural killer KHYG-1 cells to human chronic myelogenous leukemia K562 cells and colorectal tumor HCT116 cells. Furthermore, levels of mRNA expression and secretion of IFN-γ (interferon gamma) increased in KHYG-1 cells that had been treated with the six lactic acid bacteria mixture from kefir. The results suggest that the six lactic acid bacteria mixture from kefir has strong effects on natural immunity and tumor cell cytotoxicity.

Investigation of the bacteriophage community in induced lysates of undefined mesophilic mixed-strain DL-cultures using classical and metagenomic approaches

To investigate the notion that starter cultures can be a reservoir of bacteriophages (phages) in the dairy environment, strains of three DL-starters (undefined mesophilic mixed-strain starters containing Lactococcus lactis subsp. lactis biovar. diacetylactis and Leuconostoc species) were selected and induced by mitomycin C, and the whole starters were induced spontaneously as well as by mitomycin C. Frequency of induction of 17%, 26% and 12% was estimated among the isolates of the three starters, with majority of the induced phages mostly showing morphological similarity to known P335 phages, and with a fraction of them showing atypical features. Sequences of P335 quasi-species phages were found to be the most frequent entities in almost all metaviromes derived from the induced lysates. However, sequences of Sk1virus phages (previously 936 phages) were emerged as the predominant entities following spontaneous induction of one of the starters, suggesting a phage-carrier state. Sequences of other phages such as 949, 1706, C2virus (previously c2 phages) and Leuconostoc species could also be observed but with a lower relative frequency. Taken together, the majority of the P335 quasi-species phages could represent the induced viral community of the starters and the remaining phage groups mainly represent the background ambient viral community.

Изучение разнообразия ассоциаций фагов гомологичных молочнокислым бактериям

Information on the ecology of the "phage-bacterial host" system is given. The interaction of cultures of lactococci from the collection of the Siberian Research Institute of Cheese with associations of phages was investigated. Infection of sensitive cells with bacteriophage led to cell lysis, which was manifested by negative colonies on the lawn of a lactococcal culture. Characteristics of the biological properties of bacteriophages in the composition of phage associations are given (lytic activity, spectrum of lytic activity, specificity of action). Differentiation of species lysotypes of bacteriophages of mesophilic lactococci, selected at a single cheese enterprise in the Altai Territory was noted. The index of the lytic activity of the investigated phage associations ranged from 0.19 (sample of Lactococcus lactis subsp. Lactis biovar diacetylactis) to 0.24 (sample of Lactococcus lactis subsp. Lactis) from studied strains. The value of the lyotype updated coefficient for the entire array of data varied from 0.25 to 1.00. It is concluded that the specificity of cheese biotechnology together with the evolutionary and genetic determinants of the microworld predetermine a constant high risk of cell phagolysis of starter cultures. Experimental studies confirmed the need to consider the phagocyte of lactic acid bacteria in biotechnology.

Licheniocin 50.2 and Bacteriocins from Lactococcus lactis subsp. lactis biovar. diacetylactis BGBU1-4 Inhibit Biofilms of Coagulase Negative Staphylococci and Listeria monocytogenes Clinical Isolates.

BackgroundCoagulase negative staphylococci (CoNS) and Listeria monocytogenes have important roles in pathogenesis of various genital tract infections and fatal foetomaternal infections, respectively. The aim of our study was to investigate the inhibitory effects of two novel bacteriocins on biofilms of CoNS and L. monocytogenes genital isolates.MethodsThe effects of licheniocin 50.2 from Bacillus licheniformis VPS50.2 and crude extract of bacteriocins produced by Lactococcus lactis subsp. lactis biovar. diacetylactis BGBU1-4 (BGBU1-4 crude extract) were evaluated on biofilm formation and formed biofilms of eight CoNS (four S. epidermidis, two S. hominis, one S. lugdunensis and one S. haemolyticus) and 12 L. monocytogenes genital isolates.ResultsLicheniocin 50.2 and BGBU1-4 crude extract inhibited the growth of both CoNS and L. monocytogenes isolates, with MIC values in the range between 200–400 AU/ml for licheniocin 50.2 and 400–3200 AU/ml for BGBU1-4 crude extract. Subinhibitory concentrations (1/2 × and 1/4 × MIC) of licheniocin 50.2 inhibited biofilm formation by all CoNS isolates (p < 0.05, respectively), while BGBU1-4 crude extract inhibited biofilm formation by all L. monocytogenes isolates (p < 0.01 and p < 0.05, respectively). Both bacteriocins in concentrations of 100 AU/mL and 200 AU/mL reduced the amount of 24 h old CoNS and L. monocytogenes biofilms (p < 0.05, p < 0.01, p < 0.001).ConclusionsThis study suggests that novel bacteriocins have potential to be used for genital application, to prevent biofilm formation and/or to eradicate formed biofilms, and consequently reduce genital and neonatal infections by CoNS and L. monocytogenes.

Nisin is an effective inhibitor of Clostridium difficile vegetative cells and spore germination.

Clostridium difficile is the most frequently identified enteric pathogen in patients with nosocomial antibiotic-associated diarrhoea and pseudomembranous colitis. Several clinically isolated C. difficile strains are resistant to antibiotics other than metronidazole and vancomycin. Recently, bacteriocins of lactic acid bacteria have been proposed as an alternative or complementary treatment. The aim of this study was to investigate the inhibitory effect of nisin, a bacteriocin produced by several strains of Lactococcus lactis, against clinical isolates of C. difficile. Nisin Z obtained from culture of L. lactis subsp. lactis biovar. diacetylactis was tested along with commercial nisin A. The effect of nisin A on C. difficile spores was also examined. Nisin A and Z both inhibited the growth of all C. difficile isolates, and MICs were estimated at 6.2 μg ml(-1) for nisin Z and 0.8 μg ml(-1) for nisin A. In addition, C. difficile spores were also susceptible to nisin A (25.6 μg ml(-1)), which reduced spore viability by 40-50%. These results suggested that nisin and hence nisin-producing Lactococcus strains could be used to treat C. difficile-associated diarrhoea.

Process for improving the quality of direct acidified Cottage cheese

The effects of plain and fermented curd dressing ripened by single (Lactococcus lactis subsp. lactis biovar. diacetylactis) as well as mixed-strain starter cultures (L. lactis subsp. lactis; L. lactis subsp. cremoris; L. lactis subsp. lactis biovar. diacetylactis:: 1:1:1), different levels of fat (18–24%) in curd dressing and inoculation rate (1–5%) on direct acidified Cottage cheese were observed. Ripened curd dressing containing 22% fat and mixed-strain starter cultures at 3% imparted a pleasant acidic note, delicate overtones of diacetyl, improved the body and texture, visual appearance and thereby enhanced the overall quality of the product.

Influence of autochthonous lactic acid bacteria and enzymatic yeast extracts on the microbiological, biochemical and sensorial properties of Lben generic products

In this study we identified Lactococcus lactis subsp. lactis, Lc. lactis subsp. lactis biovar diacetylactis, Kluyveromices lactis and Saccharomyces cerevisiae as the dominant microorganisms of traditional Moroccan acid-alcoholic fermented milk named Lben. The low pH (3·8±0·3), lactose (16·8±3·4mg/l) and lactic acid (8·16±0·6mg/l) content indicated that a strong fermentation occurred in the traditional product which was also characterised by the substantial presence of ethanol and typical volatile carbonyl compounds (i.e., acetoin, diacetyl and acetaldehyde). Microbiological analyses of experimental Lben manufactured with selected strains (isolated from the traditional product) of Lc. lactis subsp. lactis and Lc. lactis subsp. lactis biovar. diacetylactis alone (batch A) and in combination with enzymatic extract of a K. lactis strain (batch B) indicated a good effectiveness of the starters employed (∼1010 CFU/g of lactococci after 8h of incubation) and a significant effect of the yeast enzyme extract on lactococci viability. Despite slight changes in the physicochemical characteristics of the two Lben during the 15d storage period, volatile compounds (i.e. ethanol, acetaldehyde, diacetyl and acetoin) were consistently higher in batch B. Moreover, sensorial analysis performed after 15d of storage, highlighted higher odour and flavour intensity, vegetable odour and viscosity in batch B while batch A displayed higher astringency.

Screening and identification of lactic acid bacteria isolated from sorghum silage processes in west Algeria

The lactic acid bacteria (LAB) isolated from sorghum (Sorghum bicolor. L.) silage were identified during different periods of evolution of sorghum silage in west Algeria. Morphological, physiological, biochemical and technological techniques were used to characterize lactic acid bacteria isolates. A total number of 27 representatives of lactic acid bacterial strains were retained and among them four dominant genus were identified as Lactobacillus (44%), Lactococcus (14.81%), Weissella (29.62%) and Leuconostoc (11.11%). The representative species identified were Lactobacillus brevis (25%), Lactobacillus pentosus (3.7%), Lactobacillus manihotivorans (11.11%), and Lactobacillus fermentum (3.7%). Lactococcus lactis subsp. lactis biovar. diacetylactis (14.81%), Weissella cibaria (7.2%), Weissella minor (11.11%), Weissella soli (3.7%), Weissella viridescense (7.2%) and Leuconostoc mesenteroides subsp. mesenteroides (11.11%). Only two strains of lactic acid bacteria were amylolytic. These results will enable future research on the relationship between LAB species and silage fermentation quality.