Effects of different hydrogen partial pressure on microbial protein production via simultaneous conversion of CO2 and ammonia
Hydrogen-oxidizing bacteria(HOB)can simultaneously convert ammonia and CO2 into microbial protein(MP),which has a great potential for application.This study investigated the effects of different hydrogen partial pressures on CO2 fixation,ammonia conversion and protein production in HOB system.The results showed that the HOB system was strengthened with the increment of hydrogen partial pressure.At the hydrogen partial pressure of 0.8 bar,the cell density(OD620)and the concentration of RuBP carboxylase reached the maximum vaules of OD620=0.50,concentration of enzyme was((41.27±1.20)ng·L-1,respectively.Meanwhile,the CO2 fixation rate and ammonia conversion rate also reached the highest values of 0.06 L·(L·d)-1 and 68.48％,respectively.At the hydrogen partial pressure was equal to or higher than 0.8 bar,the capacity of HOB to produce MP was significantly enhanced,and the protein yield,protein content and amino acid yield were higher than 1.3 g·L-1,68％,and 950 mg·L-1,respectively.The correlation analysis among the key factors indicated the significant linear correlations occurred between hydrogen partial pressure and CO2 fixation rate,H2 consumption rate,cell dry weight,or crude protein content in HOB system(R2＞0.8),and a significant quadratic relationship occurred between hydrogen partial pressure and ammonia conversion rate(R2=0.99).Therefore,the system operation can be optimized through appropriately increasing the hydrogen partial pressure in the process of MP production via HOB.This study could provide data support and theoretical foundation for the high efficiency and quality of MP production in practical application.
hydrogen-oxidizing bacteriahydrogen partial pressureCO2 fixationmicrobial protein
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