Isolation，identification and characterization of acidproducing strains from psychrotolerant biogas fermentation

Abstract:

Abstract:［Objective］The aim of this study was to screen acid-producing strains from the broth of psychrotolerant biogas fermentation and evaluate the acid-producing character of them.［Methods］Acid-producing strains were isolated by a medium with methyl red at 4 ℃ in Petri dishes and identified by morphology observation and 16S rRNA sequencing．Moreover，the ability of hydrolysis of starch，fermentation of carbohydrates，liquefaction of gelatin and production of catalase were studied．［Results］Two acid-producing strains (FJ-8 and FJ-15) were isolated． The result of the 16S rRNA phylogenetic tree shows that FJ-8 and FJ-15 belong to Pseudomonas sp． and Shewanella sp.，respectively． Both FJ-8 and FJ-15 could hydrolyze starch，liquidize gelatin and produce catalase． The optimum temperature for acid-producing of FJ-8 and FJ-15 is 15 ℃ and 20 ℃，respectively． After 10 days cultivation at 4 ℃，the concentration of acetic acid was 792 mg/L and 966 mg/L of FJ-8 and FJ-15 ，respectively.［Conclusion］The selected strains，FJ-8 and FJ-15，have the potential to produce acids at low temperature.