Lactic acid fermentation by cells of Lactobacillus rhamnosus immobilized in polyacrylamide gel

Abstract

The process of lactic acid fermentation of lactose to lactic acid by Lactobacillus rhamnosus ATCC 7469 has been studied. The following processes have been explored: growth kinetics, as well as lactose utilization, production of lactic acid and further degradation of lactic acid. The immobilization experiments were conducted with microbial cells entrapped in polyacrylamide gels. Gels with different ratios of the monomer (acrylamide) and the cross-linking agent (N,N¢-methylene-bis-acrylamide) have been tested. These were used in a repeat-batch process. The current processes inside and outside the gel particles were subjects of examination. The evolution of the activity of immobilized cells with repeated use showed that the particles served mainly as a donor of cells for the free culture. In all experiments a very high degree of conversion, 85-90% was observed. After several runs however, the particles were exhausted for microbial cells. A kinetic model of the process of lactic acid production was developed. This model allowed the evaluation of the effect of microbial growth and diffusion limitations inside the gel particles on the process rate and the separate contribution of the free and immobilized cells to the overall fermentation process upon multiple use.

Applications of Lactobacillus rhamnosus Spent Culture Supernatant in Cosmetic Antioxidation, Whitening and Moisture Retention Applications

“…Among lactic acid bacteria (LAB), members of the genus Lactobacillus are generally regarded as non-pathogenic because of their long history of safe use as health-promoting organisms in numerous fermented food products—e.g., dairy products, fermented vegetables, fish and sausages—as well as silage inoculants [5,7,8]. Lactobacillus rhamnosus ( L. rhamnosus ) has been shown to produce lactic acid as the only carbohydrate metabolism product [9,10].…”

Improved immobilization of Lactobacillus rhamnosus ATCC 7469 in polyacrylamide gel, preventing cell leakage during lactic acid fermentation

“…As a baseline comparison the free culture kinetics of L. rhamnosus ATCC 7469 and the processes with gels, prepared with AA/MBAA stock, presented recently (Petrov et al 2006) were used. These gels possessed high degree of cell leakage.…”

“…The processes inside and outside the gel particles were the subject of examination and a kinetic model of the lactic acid production was developed (Petrov et al 2006). However, gels prepared by the above mentioned method demonstrated a high level of cell leakage.…”

Opportunities, perspectives and limits in lactic acid production from waste and industrial by-products

“…Imobilizacija u polimerne matrice gela je često korišćena tehnika imobilizacije BMK. Kao materijali za imobilizaciju korišćeni su prirodni polimeri, kao što su Ca-alginat [84,85], agar [86], κ-karagenan [87], a od sintetskih poliakrilamid [87,88] i polivinil alkohol [89]. Za imobilizaciju u polimerne matrice gela je karakteristična ograničena difuzija supstrata i proizvoda kroz polimernu matricu što smanjuje prinos MK.…”