Optimization of upstream and downstream process parameters for cellulase-poor-thermo-solvent-stable xylanase production and extraction by Aspergillus tubingensis FDHN1

Bioresources and Bioprocessing

Table 5 Effect of various extraction solvents on xylanase recovery from the fermented sorghum straw

Name of extractant ^a	Xylanase activity (U/g)	Protein (mg/g)	Specific activity (U/mg)	Cellulase activity (U/g)
Citrate buffer (0.05 M, pH 5.0)	2,591 ± 50	24.86 ± 0.99	104.22 ± 3.55	3.26 ± 0.11
Na-citrate buffer (0.05 M, pH 6.5)	3,573 ± 22	27.96 ± 1.08	127.79 ± 2.13	4.02 ± 0.08
Double-distilled water (pH 7.0)	2,675 ± 26	26.88 ± 1.19	99.51 ± 4.67	3.83 ± 0.05
Phosphate buffer (0.05 M, pH 7.5)	3,256 ± 23	25.79 ± 0.79	126.25 ± 4.06	3.54 ± 0.14
Tris buffer (0.05 M, pH 8.0)	2,859 ± 13	23.96 ± 0.96	119.32 ± 3.24	4.87 ± 0.17
Tween-80 (0.2% v/v)	3,166 ± 10	25.47 ± 0.67	124.30 ± 3.00	3.09 ± 0.06
NaCl (1.0% w/v)	2,416 ± 18	26.88 ± 1.07	91.93 ± 2.67	4.00 ± 0.13

^aSSF was carried using 9 g sorghum straw under optimized physiological (at 5-day incubation, 1:5 (w/v) substrate/moisture ratio, pH 6.0 and 40°C) and nutritional conditions (xylose 0.3%, gelatine and NaNO₃ both at 0.05 g N equivalent in 50 mL medium). For xylanase recovery, the fermented sorghum straw was mixed with the solvents separately at an extractant/solid ratio of 10:1 (v/w) and agitated at 120 rpm for 60 min at 37°C. The data presented are the mean values of three replicates with the standard deviations.