Polyphasic Characterisation of Non-Starter Lactic Acid Bacteria from Algerian Raw Camel’s Milk and Their Technological Aptitudes

Abstract

Research background. Consumption of spontaneously fermented camel´s milk is usual in Algeria, making it a feasible source of diverse lactic acid bacteria (LAB) with the potential to be used as adjunct cultures to improve quality and safety of dairy fermented products. Experimental approach. Twelve raw camel´s milk samples were used as source of indigenous LAB, which were further characterised by examining 39 phenotypic traits with technological relevance. Results and conclusions. Thirty-five non-starter LAB (NSLAB) were isolated from 12 Algerian raw camel's milk samples and they were microbiologically, biochemically and genetically characterised. Some isolates showed proteolytic activity, acidifying capacity, the ability to use citrate, and to produce dextran and acetoin. Ethanol, acetaldehyde, methyl acetate, acetoin and acetic acid were the major volatile compounds detected. Cluster analysis performed using the UPGMA method, and based on the thirty-nine phenotypic characteristics investigated, reflected the microbial diversity that can be found in raw camel´s milk. Novelty and scientific contribution. The isolated strains, from a non-typical source, showed interesting technological traits to be considered as potential adjunct cultures. Cluster analysis based on the phenotypic characteristics examined turned out to be a useful tool for the typification of isolates when no genetic information is available. These findings may be of use towards an industrialised production of camel's milk dairy products.

GABA-Producing Lactococcus lactis Strains Isolated from Camel’s Milk as Starters for the Production of GABA-Enriched Cheese

“…The Lactococcus isolates were identified at the species level by 16S rRNA gene sequencing following the protocol described in Saidi et al [ 29 ].…”

“…The proteolytic activity of the GABA-producing L. lactis strains was examined by a qualitative method on Plate Count Agar (PCA) (Oxoid) supplemented with 2% UHT skimmed cow’s milk as described by Saidi et al [ 29 ]. In addition, proteolytic activity was quantitatively determined using the O-phthaldialdehyde (OPA) method following the protocol described by the same author.…”

“…Dextran production was determined using Mayeux, Sandine and Elliker (MSE) agar medium rich in sucrose as described in Saidi et al [ 29 ].…”

“…To determine the production of volatile compounds, UHT skimmed cow’s milk was inoculated with individual overnight cultures of the GABA-producing L. lactis strains at 1% ( v / v ) and incubated for 24 h at 30 °C. A head space gas chromatograph (Agilent Technologies, Wilmington, DE, USA) connected to a mass spectrophotometer detector (HS/GC/MS) was used to quantify volatile compounds [ 29 ]. They were quantified as the normalized value of their chromatogram peak area using cyclohexanone (3.6 µg/mL) as an internal standard, which was given a value of 100.…”

“…To determine the antimicrobial activity of the isolates, well-diffusion assays were performed according to Saidi et al [ 29 ]. The strains used as microbial indicators are listed in Table 1 .…”