Submerged fermentation as a suitable solution to produce humic and fulvic acids from sugarcane bagasse

Abstract

Humic and fulvic acids are valuable compounds that are produced from sugarcane bagasse using Solid-State Fermentation (SSF) and Submerged Fermentation (SmF). Initially, fourteen treatments were examined to determine the most prominent one with a proper C/N ratio. BFFU (Bagasse + Filter cake + Fungi booster + Urea) is regarded as the most e ective mixture. The results obtained from SSF using BFFU treatment included 3.96 and 2.36% dry matters for Humic Acid (HA) and Fulvic Acid (FA), respectively. Optimal treatment and fermentation systems were implemented using two di erent SmF bioreactor volumes (60 and 1000 liter) to determine the optimal condition for higher yield. In contrast with the SSF, production yield in the SmF system resulted in a higher yield within a shorter processing time (36 days in SmF instead of 70 days in SSF). These obtained values were almost three times more than the SSF results in the range of 12.84 to 7.91% DM over a period of 36 days. However, the production rate was slightly higher when using a 1000-liter Continuous Stirred-Tank Reactor (CSTR) (14.25 and 8.39% DM over 35 days) than that in regular conditions. The results from Fourier Transform Infrared Spectroscopy (FTIR) pointed to some structural similarities between the SB-derived HA and FA in the present study and those of their commercial counterparts.