Purification of lipase produced by L. mesenteroides subsp. mesenteroides ATCC 8293 was conducted for the first time using a novel aqueous two-phase system (ATPS) composed of Triton X-100 and maltitol. The partitioning of lipase was optimized according to several parameters including pH, temperature, and crude load. Results showed that lipase preferentially migrated to the Triton X-100 rich phase and optimum lipase partitioning was achieved in ATPS at TLL of 46.4% and crude load of 20% at 30 °C and pH 8, resulting in high lipase purification factor of 17.28 and yield of 94.7%. The purified lipase showed a prominent band on SDS-PAGE with an estimated molecular weight of 50 kDa. The lipase was stable at the temperature range of 30⁻60 °C and pH range of 6⁻11, however, it revealed its optimum activity at the temperature of 37 °C and pH 8. Moreover, lipase exhibited enhanced activity in the presence of non-ionic surfactants with increased activity up to 40%. Furthermore, results exhibited that metals ions such as Na⁺, Mg2+, K⁺ and Ca2+ stimulated lipase activity. This study demonstrated that this novel system could be potentially used as an alternative to traditional ATPS for the purification and recovery of enzymes since the purified lipase still possesses good process characteristics after undergoing the purification process.
Kefir is a fermented milk obtained by fermenting milk with kefir grains. The chemical composition ofdairy and non-dairy sources may affect the growth and characterisation of lactic acid bacteria (LAB). In this study, different sources of milk (cow milk) and non-dairy milk (soymilk and coconut milk) were used as the fermentation media for kefir products. The objectives of the study were to isolate and characterise LAB from kefir drink produced from dairy and non-dairy milk. LAB was isolated using different cultural methods, such as MRS Agar, MRS with 0.8% CaCO3, and M17 Agar. The characteristics of the LAB isolates were determined using morphological, biochemical tests and the API 50 CHL kit. The physicochemical composition of the samples was determined using titratable acidity and pH level. Sensory evaluation of the kefir drink samples was also carried out. Results confirmed that the isolates were identified as Lactobacillus buchneri, Lactobacillus brevis 1, Leuconostoc mesenteroides, Lactobacillus acidophilus 3and Lactobacillus plantarum 1. The L. buchneri, L. brevis, Leu. mesenteroides and L. acidophilus are heterofermentative bacteria, whereas L. plantarum is a homofermentative bacterium. Four LAB isolates have the potential to be used as probiotic strains due to their high resistant to low pH and bile salt. The sensory scores of these products range between 5.00 and 8.00 in the 9-point hedonic scale. Most of the sensory panelists preferred cow milk kefir (p < 0.05) compared with coconut milk kefir and soy milk kefir during the sensory evaluation of all attributes. Meanwhile, the preference between coconut milk kefir and soy milk kefir was similar (p>0.05) in all attributes. Therefore, this study will be useful for probiotic manufacturers in the production of alternative probiotic drinks using dairy and non-dairy milk.