This study aimed to examine the influence of adding an oxygen vector, n-dodecane, on hyaluronic acid (HA) production by batch culture of Streptococcus zooepidemicus. Owing to the high viscosity of culture broth, microbial HA production during 8-16 h was limited by the oxygen transfer coefficient K(L)a, which could be enhanced by adding n-dodecane. With the addition of n-dodecane to the culture medium to a final concentration of 5% (v/v), the average value of K(L)a during 8-16 h was increased to 36+/-2 h(-1), which was 3.6 times that of the control without n-dodecane addition. With the increased K(L)a and dissolved oxygen (DO) by adding 5% (v/v) of n-dodecane, a 30% increase of HA production was observed compared with the control. Furthermore, the comparison of the oxygen mass transfer in the absence and presence of n-dodecane was conducted with two proposed mathematical models. The use of n-dodecane as an oxygen vector, as described in this paper, provides an efficient alternative for the optimization of other aerobic biopolymer productions,where K(L)a is usually a limiting factor.