To investigate the effect of buffer and starting culture pH on the yields and mechanics of BC, all media used 2 wt% glucose, 0.5 wt% peptone, and 0.5 wt% yeast extract as the carbon and nitrogen source, and the composition of the buffer is shown in Table 1 [33 (link), 34 (link)]. The starting pH gradients were set at 4.60, 5.00, 5.40, and 5.80 respectively. The control group was prepared by removing the phosphate and citrate in the original recipe of HS medium.
The concentration of glucose and gluconic acid in the culture medium was detected by using a Glucose Assay Kit and D-Gluconate/D-Glucono-d-lactone Assay Kit (both from Megazyme, Ireland) respectively. Following the manufacturer’s protocol, samples were mixed with deionized water at the ratio of 1:9 (v/v). The attached bacterial cells were removed by centrifuging at 10,000 ×g for 10 min. The absorbance of the specimens was measured by using an ultraviolet (UV) spectrophotometer (Evolution 200, Thermo Fisher, USA) to calculate the concentration of glucose or gluconic acid in the scale-up inoculation media.
The concentration of glucose and gluconic acid in the culture medium was detected by using a Glucose Assay Kit and D-Gluconate/D-Glucono-d-lactone Assay Kit (both from Megazyme, Ireland) respectively. Following the manufacturer’s protocol, samples were mixed with deionized water at the ratio of 1:9 (v/v). The attached bacterial cells were removed by centrifuging at 10,000 ×g for 10 min. The absorbance of the specimens was measured by using an ultraviolet (UV) spectrophotometer (Evolution 200, Thermo Fisher, USA) to calculate the concentration of glucose or gluconic acid in the scale-up inoculation media.