High productivity bioethanol fermentation by immobilized Saccharomyces bayanus onto carboxymethylcellulose-g- poly(N-vinyl-2-pyrrolidone) beads

Figures & data

Table I. Grafting yield and elemental analysis results for CMC and grafted CMC.

Copolymer	Monomer concentration (M)	GY (%)	C (%)	H (%)	N (%)
CMC	–	0	35.32	5.40	–
CMC-g-PVP1	0.27	20	40.85	5.95	2.78
CMC-g-PVP2	0.46	24	42.16	6.30	3.36
CMC-g-PVP3	0.65	32	44.35	6.49	4.50

Figure 1. Change in the swelling degree of CMC beads and CMC-g-PVP beads with time.

Figure 2. SEM photographs of Saccharomyces bayanus immobilized: (a) CMC; (b) CMC-g-PVP.

Table II. Physical properties and immobilization yield of cell immobilized beads.

	CMC	CMC-g-PVP1	CMC-g-PVP2	CMC-g-PVP3
Bead diameter before fermentation (mm)	2.941	3.216	3.304	3.563
Bead diameter after fermentation (mm)	4.134	4.327	4.682	4.875
Pore size (nm)	3.589	4.431	5.153	5.876
Pore volume (cm^3/g bead)	1.390	1.426	1.820	2.266
Free dry mass (g L^−1)	0.621	0.708	0.815	0.891
Immobilized dry mass (g L^−1)	3.163	4.244	5.392	6.943
Immobilization yield (%)	84	86	87	89

Figure 3. Change of ethanol production with glucose consumption when CMC-g-PVP₃ was used with the initial 200 g/L of glucose concentration.

Table III. Ethanol production and cell concentration results of cell immobilized beads

	Final ethanol concentration (g l^−1)	Ethanol productivity (g L^−1 h^−1)	Ethanol yield (g g^−1)
CMC	92.12	7.68	0.461
CMC-g-PVP1	94.43	7.87	0.472
CMC-g-PVP2	96.11	8.01	0.481
CMC-g-PVP3	98.78	8.23	0.494

Figure 4. Change of ethanol production and ethanol productivity with initial glocose concentration.

Table IV. The effect of crosslinker concentration on ethanol productivity.

Crosslinker concentration (M)	Ethanol productivity (g L^−1 h^−1)
0.1	8.14
0.3	7.90
0.5	7.64

Figure 5. Reusability of Saccharomyces bayanus immobilized beads.