A medium supplemented with vegetable extract used for cellulose production of Rhodococcus SP. MI 2

Abstract

In this study, the most suitable vegetable extract was screened to use as non-conventional nutrient sources for cellulose production of Rhodococcus sp. MI 2. SH medium or a synthetic medium was used as a conventional or control medium. Cha-poo (Piper sarmentosum Roxb.) and sweet potato (Ipomoea batatas Lam.) were 2 out of 14 vegetable extracts chosen as medium supplements. Rhodococcus sp. MI 2 gave the highest cellulose yield in a medium supplemented with Cha-poo extract. The optimum culture conditions in the medium supplemented with Cha-poo extract at room temperature (25^o C) under static condition were 5% (v v^-1) inoculum size, a 6 -day -incubation period, pH 3, 3% sucrose, and 0.5% (NH₄)₂SO₄. The cellulose yield in the medium supplemented with Cha-poo extract was increased about 3 times (6.83 g L^-1 during 6 days) higher than that obtained before optimizing (2.39 g L^-1 during 6 days). The medium supplemented with Cha-poo extract cost one quarter (0.5 USD L^-1 of medium) of the SH medium (1.9 USD L^-1 of medium). The structure of the microfibrils of cellulose produced by Rhodococcus sp. MI 2 in a medium supplemented with Cha-poo extract observed by SEM had larger, less crowded fibrils than those produced in the medium supplemented with sweet potato extract. In addition, the microfibrils of the former had many beehive shaped knots whereas those of the latter had mantle-like surrounding the fibrils.