BiodecomposingSpirulina platensisby ade novodesignedBacillus subtilis-based method to develop a medium for the high cell-density cultivation ofEscherichia coliin batch mode

Abstract

High cell-density cultivation (HCDC) is fundamental to basic research and industrial applications, especially in batch mode. However, limited media are available for batch culture of HCDC, because the media for batch culture must contain extremely sufficient nutrients on the one hand and few or even no substrates to generate detrimental metabolite on the other hand to attain HCDC. Spirulina platensis (SP), a new media material, is considered ideal for the development of such media. Here, we develop a biolysis method for SP degradation based on the cultivation supernatant of Bacillus subtilis and extensively demonstrate its higher degradation (indicated by the production of more small peptides and free amino acids) and cultivation effectiveness with three other methods. Based on its SP hydrolysates, a modified SP-based broth (MSP) is then formulated. Tests on Escherichia coli K-12 show that MSP achieves HCDC with several benefits: (i) its maximum optical density at 600 nm is ~16.67, significantly higher than that of Luria-Bertani (LB) broth (only ~6.30); (ii) MSP requires only 36 h to reach peak growth, much faster than that of LB (48 h); (iii) its maximum growth (1.12 ± 0.01 h−1) is significantly higher than that of LB (0.20 ± 0.00 h−1); (v) MSP initiates growth immediately after inoculation (lag time <0), comparable to LB; (iv) the number of viable cells in MSP is high (~2.16 × 1011ml-1), ~10.19 times the amount in LB. Consequently, we envision MSP will become the first choice for E. coli HCDC batch culture in the future.