Fermentation is an important industrial process. It is not only used to make alcoholic beverages, but can also produce, e.g., lactic acid. In industry, it is usually important to create aseptic conditions to avoid contamination with other bacteria than the ones used for the fermentation process. This often requires high temperatures for sterilization or the use of antibiotics. An alternative is “open fermentation”, which uses harsh conditions that only the selected fermenting microorganisms can withstand.

Jian Zhang, Jie Bao, East China University of Science and Technology, Shanghai, China, Leonardo da Costa Sousa, Michigan State University, East Lansing, USA, and colleagues have developed a process for the open fermentation of lignocellulosic materials to produce lactic acid. The team used the bacterium Pediococcus acidilactici, which produces antibacterial peptides, so-called bacteriocins, that can kill other bacteria. To produce the lactic acid, corn stover, i.e., stalks, leaves and other waste material left after corn harvest, was fermented using both open fermentation and traditional aseptic conditions as a control. The team also performed contamination experiments, where they introduced other bacteria to the fermentation mixture.

The researchers found that antibacterial peptides were produced during the fermentation process and effectively prevented the growth of undesirable bacteria. The method achieved high yields of lactic acid during open fermentation, without a need for sterilization or antibiotics. According to the team, the antibacterial peptides do not lead to the development of resistant bacteria, in contrast to antibiotics.

• Antibacterial Peptide Secreted by Pediococcus acidilactici Enables Efficient Cellulosic Open l-Lactic Acid Fermentation,
  Abdul Sattar Qureshi, Jian Zhang, Leonardo da Costa Sousa, Jie Bao,
  ACS Sustainable Chem. Eng. 2017.
  DOI: 10.1021/acssuschemeng.7b02212