Mass production of heteropolysaccharide-7 (PS-7) by Beijerinckia indica HS-2001 with soybean pomace as a nitrogen source

Cell growth and the production of heteropolysaccharide-7 (PS-7) by Beijerinckia indica HS-2001, a UV-induced mutant of B. indica ATCC 21423, were enhanced with limited concentrations of ammonium nitrate and bacto-peptone. The production of PS-7 with 0.6 g l−1 ammonium nitrate and 0.5 g l−1 bacto-peptone as nitrogen sources in a flask scale was 6.28 g l−1 for 72 h, whereas that with 0.6 g l−1 ammonium nitrate and 1.0 g l−1 soybean pomace substituted for bacto-peptone was 6.88 g l−1. Productions of PS-7s with 0.6 g l−1 ammonium nitrate and 1.0 g l−1 soybean pomace in a 7 l bioreactor and a 100 l bioreactor for 42 h were 6.89 g l−1 and 8.20 g l−1, respectively, which were higher than that with the same concentration of ammonium nitrate and 0.5 g l−1 bacto-peptone in a 7 l bioreactor. Based on the gas chromatogram and FTIR spectra, PS-7 produced with soybean pomace was identified to have the same monomeric components, glucose and rhamnose, and the same molar ratios as PS-7 produced with bacto-peptone. In this study, soybean pomace was developed as a substrate substituted for bacto-peptone, which can reduce the cost for preparing a medium to produce PS-7 and also reduce environmental contamination caused by the disposal of agro-industrial byproducts.