Bioelectrochemical Mn(II) leaching from manganese ore by Lactococcus lactis SK071115

Area of Science:

• Biotechnology
• Electrochemistry
• Microbiology

Background:

• Lactate production in L. lactis is influenced by growth medium components like nitrate and manganese.
• Manganese(IV) reduction to manganese(II) by L. lactis was investigated for its potential in bioremediation or bio-mining.

Purpose of the Study:

• To investigate the electrochemical reduction of manganese(IV) to manganese(II) using L. lactis and a neutral red cathode.
• To enhance manganese(II) production through electrochemical assistance for bacterial metabolism.

Main Methods:

• Cyclic voltammetry was used to study the electrochemical reactions of L. lactis with manganese species using neutral red as an electron mediator.
• A modified graphite felt cathode with neutral red (NR-cathode) was developed to provide electrochemical reducing equivalence.
• L. lactis was used in both cell-free extract and immobilized forms (L-NR-cathode) to catalyze manganese reduction.

Main Results:

• Electrochemical reduction conditions increased manganese(II) generation by L. lactis cell-free extract approximately 4-fold compared to control.
• Immobilized L. lactis on the NR-cathode showed over 4-fold increase in manganese(II) production under electrochemical reduction.
• Citrate addition further enhanced manganese(II) production, with cumulative production from manganese ore reaching 16,000 mg/l under optimal electrochemical conditions over 30 days.

Conclusions:

• The NR-cathode effectively generates electrochemical reduction, activating the biochemical reduction of manganese(IV) to manganese(II) by L. lactis.
• Electrochemical enhancement significantly boosts the efficiency of manganese biotransformation by L. lactis.
• This approach holds promise for biotechnological applications involving manganese recovery or detoxification.