Enhanced Microbial Diversity Attained Under Short Retention and High Organic Loading Conditions Promotes High...

Area of Science:

• Biotechnology and Bioengineering
• Environmental Science
• Microbiology

Background:

• Volatile fatty acid (VFA) production optimization is hindered by long hydraulic retention times (HRTs), limiting productivity and promoting VFA degradation.
• The combined effects of pH and HRT on VFA yields and process efficiency require further investigation.

Purpose of the Study:

• To investigate the impact of pH and short HRTs on VFA production, microbial community structure, and hydrolysis/acidification efficiency.
• To evaluate VFA yields and process optimization in continuous stirred-tank reactors (CSTRs) using carbohydrate-rich feedstock.

Main Methods:

• Utilized continuous stirred-tank reactors (CSTRs) fed with carrot residue pulp at controlled temperatures (25 °C).
• Investigated varying hydraulic retention times (HRTs) and organic loading rates (OLRs) under specific pH conditions (pH 5.1).
• Analyzed microbial community structure, hydrolysis efficiency, and acidification efficiency.

Main Results:

• Operating at an 11-day HRT and 4.4 g COD·L^-1·d^-1 OLR achieved ~45% VFA bioconversion efficiency and 84% acidification efficiency.
• Shorter HRT and higher OLR enhanced hydrolysis efficiency to 60% and increased microbial diversity.
• Stable VFA production, dominated by acetic and butyric acids, was maintained without compromising VFA profile or productivity.

Conclusions:

• Shorter HRTs and higher OLRs can improve reactor space-time yield for VFA production, challenging the necessity of long retention times.
• Optimized operational conditions, including pH and HRT, enhance microbial activity and VFA yields.
• This study provides a foundation for more efficient VFA production processes from complex organic wastes.