High D(−) lactic acid levels production by Sporolactobacillus nakayamae and an efficient purification

Draft genome sequencing of Sporolactobacillus terrae SBT-1, an efficient bacterium to ferment concentrated sugar to D-lactic acid

Recently, the industrial-scale development of microbial D-lactic acid production has been discussed. In this study, the efficiency of the new isolate Sporolactobacillus terrae SBT-1 for producing D-lactic acid under challenge conditions was investigated. The isolate SBT-1 exhibited superior activity in fermenting a very high glucose or sucrose concentration to D-lactic acid compared to the other S. terrae isolates previously reported in the literature; therefore, SBT-1 could overcome the limitations of effective lactic acid production. In batch cultivation using 360 g/L glucose, SBT-1 produced 290.30 g/L D-lactate with a sufficiently high glucose conversion yield of 86%, volumetric productivity of 3.02 g/L h, and optical purity of 96.80% enantiomer excess. SBT-1 could also effectively utilize 440 g/L sucrose as a sole carbon source to produce 276.50 g/L lactic acid with a conversion yield of 90%, a production rate of 2.88 g/L h, and an optical purity of 98%. D-Lactic acid fermentation by two other related producers, S. inulinus NRIC1133^T and S. terrae NRIC0357^T, was compared with fermentation by isolate SBT-1. The experimental data revealed that SBT-1 possessed the ability to ferment relatively high glucose or sucrose concentrations to D-lactic acid without obvious catabolite repression and byproduct formation compared to the two reference strains. In draft genome sequencing of S. terrae SBT-1, the results provided here can promote further study to overcome the current limitations for the industrial-scale production of D-lactic acid.

Efficient Conversion of Agroindustrial Waste into D(-) Lactic Acid by Lactobacillus delbrueckii Using Fed-Batch Fermentation

PURPOSE

The goal of this paper is to describe the green conversion of agricultural waste products, such as molasses and corn steep liquor, into large amounts of D(-) lactic acid using a facilitated multipulse fed-batch strategy and affordable pH neutralizer. This is a very low-cost process because there is no need for hydrolysis of the waste products. The fed-batch strategy increases lactic acid productivity by avoiding inhibition caused by a high initial substrate concentration, and the selected controlling agent prevents cell stress that could be caused by high osmotic pressure of the culture media.

METHODS

The effects of different carbon and nitrogen sources on lactic acid production were investigated, and the best concentrations of the medium components were determined. To optimize the culture conditions of the Lactobacillus delbrueckii strain, the effects of pH control, temperature, neutralizing agent, agitation, and inoculum size in batch cultures were investigated. Fed-batch strategies were also studied to improve production and productivity.

RESULT

A high titer of D(-) lactic acid (162g/liter) was achieved after 48 hours of fermentation. Productivity at this point was 3.37 g/L·h. The optimum conditions were a temperature of 39°C, pH 5.5 controlled by the addition of Ca(OH)2, agitation at 150 rpm, and inoculum size of 25% (v/v).

CONCLUSION

The production of high optical purity D(-) lactic acid through L. delbrueckii fermentation with molasses and corn steep liquor is a promising economical alternative process that can be performed on the industrial scale.

Steps Toward High-Performance PLA: Economical Production of d-Lactate Enabled by a Newly Isolated Sporolactobacillus terrae Strain

Optically pure d-lactate production has received much attention for its critical role in high-performance polylactic acid production. However, the current technology can hardly meet the comprehensive demand of industrialization on final titer, productivity, optical purity, and raw material costs. Here, an efficient d-lactate producer strain, Sporolactobacillus terrae (S. terrae) HKM-1, is isolated for d-lactate production. The strain HKM-1 shows extremely high d-lactate fermentative capability by using peanut meal, soybean meal, or corn steep liquor powder as a sole nitrogen source; the final titers (205.7 g L-1 , 218.9 g L-1 , and 193.9 g L-1 , respectively) and productivities (5.56 g L-1  h-1 , 5.34 g L-1  h-1 , and 3.73 g L-1  h-1 , respectively) of d-lactate reached the highest level ever reported. A comparative genomic analysis between S. terrae HKM-1 and previously reported d-lactate high-producing Sporolactobacillus inulinus (S. inulinus) CASD is conducted. The results show that many unrelated genetic features may contribute to the superior performance in d-lactate production of S. terrae HKM-1. This d-lactate producer HKM-1, along with its fermentation process, is promising for sustainable d-lactate production by using agro-industrial wastes.

High-titer and productivity of l-(+)-lactic acid using exponential fed-batch fermentation with Bacillus coagulans arr4, a new thermotolerant bacterial strain

Bacillus coagulans arr4 is a thermotolerant microorganism with great biotechnological potential for l-(+)-lactic acid production from granulated sugar and yeast extract. The highest l-(+)-lactic acid production was obtained with Ca(OH)₂. The maximum production of l-(+)-lactic acid (206.81 g/L) was observed in exponential feeding using granulated sugar solution (900 g/L) and yeast extract (1%) at 50 °C, pH 6.5, and initial granulated sugar concentration of 100 g/L at 39 h. 5.3 g/L h productivity and 97% yield were observed, and no sugar remained. Comparing the simple batch with exponential fed-batch fermentation, the l(+) lactic acid production was improved in 133.22% and dry cell weight was improved in 83.29%, using granulated sugar and yeast extract. This study presents the highest productivity of lactic acid ever observed in the literature, on the fermentation of thermotolerant Bacillus sp. as well as an innovative and high-efficiency purification technology, using low-cost substances as Celite and charcoal. The recovery of lactic acid was 86%, with 100% protein removal, and the fermentation medium (brown color) became a colorless solution.