Graphical abstract This study aimed to investigate parameters affecting the electrospinning of poly (vinyl alcohol) (PVA)/kefiran composite nanofibers. Accordingly, PVA/kefiran composite nanofibers were produced using the electrospinning of PVA, kefiran blend solutions under various electrospinning parameters (such as applied voltage, nozzle-to-collector distance, and polymer injection rate), and solution parameters (such as the ratio of polymers). PVA and kefiran solutions were prepared in 8% and 6% w/w, respectively. Kefiran was blended with PVA solution in different proportions: 70:30, 60:40, 50:50, 40:60, and 30:70. According to the scanning electron microscope (SEM) images, kefiran mixed with PVA in 40:60 ratios produced the best result in nanofiber production. Then, device parameters such as voltage (12, 15, 18, and 20 kV), distance (120, 150, 170, and 200 mm), and polymer injection rates (1, 1.5, 2, and 2.5 mL/h) were changed. The investigation of SEM images showed that the optimal condition for the fabrication of nanofibers was 18 kV, 200 mm, and 1 mL/h. The nanofibers produced in the optimal condition were uniform without knots or adhesion in a small diameter. It was also found that concentration can be regarded as the most effective parameter affecting the diameter of nanofibers. Moreover, the transmission electron microscopy (TEM) image proved that phase separation did not occur between the two polymers. Kefiran biopolymer extracted from fermented milk was used in fabrication of PVA/kefiran composite nanofibers using the electrospinning method.

The kefiran/polyvinyl alcohol and polyvinyl pyrrolidone nanofibers were effectively fabricated for the first time using electrospinning of poly(vinyl alcohol), poly(vinyl pyrrolidone) and kefiran blend solution. The effect of solution parameters, such as kefiran concentration and poly(vinyl alcohol)/poly(vinyl pyrrolidone) mixing ratio, were considered. The parameters' effects, such as voltage, nozzle-to-collector distance and feeding rate on nanofibers morphology, were also checked by the scanning electron microscopy images. After changing the parameters on different steps, designed by the chemo metrics software, the finest nanofibers were produced in the following conditions: 2% kefiran concentration, 30/70 kefiran/polymer mixing ratio, 12 kV voltage, 200 mm needle-to-collector distance and 0.5 (mL/h) polymer injection rate. The nanofibers produced in these conditions were uniform without knots or adhesion in the lowest diameter of 156 nm. Kefiran concentration and kefiran/polymer mixing ratio were found as the most effective parameter in the morphology and diameter size of the nanofibers. The attenuated total reflectance (ATR-Ft-IR), atomic force spectroscopy, differential scanning calorimeters and thermal gravimetric analysis were used to investigate molecular structures, threedimensional morphology and heating properties of the nanofibers, respectively.