Non-Sterilized Fermentative Production of Polymer-Grade L-Lactic Acid by a Newly Isolated Thermophilic Strain Bacillus sp. 2–6

Abstract

BackgroundThe demand for lactic acid has been increasing considerably because of its use as a monomer for the synthesis of polylactic acid (PLA), which is a promising and environment-friendly alternative to plastics derived from petrochemicals. Optically pure l-lactic acid is essential for polymerization of PLA. The high fermentation cost of l-lactic acid is another limitation for PLA polymers to compete with conventional plastics.Methodology/Principal FindingsA Bacillus sp. strain 2–6 for production of l-lactic acid was isolated at 55°C from soil samples. Its thermophilic characteristic made it a good lactic acid producer because optically pure l-lactic acid could be produced by this strain under open condition without sterilization. In 5-liter batch fermentation of Bacillus sp. 2–6, 118.0 g/liter of l-lactic acid with an optical purity of 99.4% was obtained from 121.3 g/liter of glucose. The yield was 97.3% and the average productivity was 4.37 g/liter/h. The maximum l-lactic acid concentration of 182.0 g/liter was obtained from 30-liter fed-batch fermentation with an average productivity of 3.03 g/liter/h and product optical purity of 99.4%.Conclusions/SignificanceWith the newly isolated Bacillus sp. strain 2–6, high concentration of optically pure l-lactic acid could be produced efficiently in open fermentation without sterilization, which would lead to a new cost-effective method for polymer-grade l-lactic acid production from renewable resources.

Enhanced production of histamine dehydrogenase by <i>Natrinema gari</i> BCC 24369 in a non-sterile condition

“…gari BCC 24369, an economical and simple enzyme production of HADH could be carried out under a non-sterile condition. In practice, non-sterilization means a lower cost due to the obviation of sterilization equipment, lower energy consumption, and a decrease of labor costs (Oren, 2006;Qin et al, 2009). The objectives of this study were to optimize the culture conditions for HADH production by Nnm.…”

Genome Sequence of the Thermophilic Strain Bacillus coagulans2-6, an Efficient Producer of High-Optical-Purity l -Lactic Acid

“…Because of stable high performance in the utilization of renewable resources and nonsterilization fermentation at high temperature, the thermophilic B. coagulans strains have been suggested to be superior producers of lactic acid (11,13). In addition to the production of lactic acid, B. coagulans has also been found to be a source of many other commercially valuable products, such as thermostable enzymes and coagulin, an antimicrobial peptide (6).…”

“…However, little genetic information is known. Here, we present the genome sequence of B. coagulans strain 2-6, which is an efficient producer of high-optical-purity L-lactic acid with the advantages of high carbon efficiency, less by-product formation, and thermotolerance (13).…”

Draft Genome Sequence of Sporolactobacillus inulinus Strain CASD, an Efficient D-Lactic Acid-Producing Bacterium with High-Concentration Lactate Tolerance Capability

“…Besides its versatile applications in the food, pharmaceutical, textile, and leather industries, lactic acid is also a building block for biodegradable plastic, mainly poly(L-lactic acid), which has gained substantial attention in the new wave of industrial biotechnology (7,4). The development of a stereocomplex of poly(L-lactic acid) and poly(D-lactic acid) is considered an advance in poly(lactic acid) modification, in which the melting point of this stereocomplex could reach the same temperature as that of other petroleum-based polymers (3).…”