EFFECTS OF IMMOBILIZATION IN Ba-ALGINATE ON NITRILE-DEPENDENT OXYGEN UPTAKE RATES OF CANDIDA GUILLIERMONDII

Abstract

Yeast cells immobilized by entrapment in Ba-alginate gel were investigated for growth pattern and respiratory activity. The oxygen uptake rates (OUR) of cells entrapped in gels with 4% alginate were 5.2 and 23% lower than the OUR of 2% alginate and free cells, respectively. The mass-transfer resistance offered by the matrix and growth of the entrapped cells determine a gradient of nutrients throughout the gel which is responsible for both a lower specific growth rate of immobilized cells with respect to that of free ones, and a heterogeneous biomass distribution, with progressively increasing cellular density from the inside to the outside of the matrix. Gel-matrix polymer concentration affected the maximum oxygen uptake of immobilized growing yeast cells.

Nitrile Metabolizing Yeasts

“…As expected, the oxygen uptake rate (OUR) of yeasts cells decreases upon immobilization which becomes more pronounced with increase in alginate concentration in beads (Dias et al, 2001b ). It is worth mentioning that upon immobilization, yeasts cells were able to hydrolyze some additional nitriles (acrylonitrile, Adiponitrile, benzonitrile, 2-cyanopyridine, 3-cyanopyridine, 4-cyanopyridine and glutaronitrile) and amides (adipamide, acrylamide, benzamide, glutaramide, succinamide) which free cells could not (Dias et al, 2001b ). This shift in substrate affinity of yeast cells upon immobilization can be explained on the basis of changed microenvironment in the matrix around the yeast cells that favors transport of such nitriles and amides into the cells.…”

“…These researchers have studied the impact of alginate and barium chloride concentration on bead formation and worked out optimum concentration of alginate and barium chloride for immobilization of yeast cells. As expected, the oxygen uptake rate (OUR) of yeasts cells decreases upon immobilization which becomes more pronounced with increase in alginate concentration in beads (Dias et al, 2001b ). It is worth mentioning that upon immobilization, yeasts cells were able to hydrolyze some additional nitriles (acrylonitrile, Adiponitrile, benzonitrile, 2-cyanopyridine, 3-cyanopyridine, 4-cyanopyridine and glutaronitrile) and amides (adipamide, acrylamide, benzamide, glutaramide, succinamide) which free cells could not (Dias et al, 2001b ).…”

Production of Poly-γ-Glutamate (PGA) Biopolymer by Batch and Semicontinuous Cultures of Immobilized Bacilluslicheniformis strain-R

“…The results also revealed the possible production PGA biopolymer by entrapped cells. However, the fluctuation in the amount of PGA produced by Bacillus cells entrapped in various gel matrices as well as during the use of different gel beads concentrations attributed to variation in aeration and diffusion of nutrient in the immobilized cell system (9, 27, 34, 35). Interestingly, polysacchrides biopolymers were successfully produced by entrapped microbial cells.…”

An Evaluation of Different Bioreactor Configurations with Immobilized Yeast for Bioethanol Production

“…Such better performance in fermentation medium mixing observed in the STR could have lead to an improvement in the mass transfer between the medium (substrate and nutrients) and the immobilized cells. According to Dias et al, (2001) the mass-transfer resistance offered by the matrix and growth of the entrapped cells determine a gradient of nutrients throughout the gel, which is responsible for both a lower specific growth rate of immobilized cells with respect to that of free ones. Efficient mixing, like that offered by STR, can lead to the reduction of the diffusion coefficient of different substances towards the interior of the gel capsules; such phenomenon has been clearly observed in this paper.…”

“…According to Dias et al, (2001) in the practical utilization of living cells entrapped in synthetic gel, diffusion of essential nutrients, oxygen transfer, physical and chemical properties of the gel and immobilization procedure are the important factors affecting microbial metabolism and the efficiency of the system. Although immobilized cells have received a lot of attention, literature results are not uniform, but vary according to the type of microorganism, of immobilizing matrix and of productive system.…”