Comparative Transcriptome Analysis Reveals Different Molecular Mechanisms of Bacillus coagulans 2-6 Response to Sodium Lactate and Calcium Lactate during Lactic Acid Production

Abstract

Lactate production is enhanced by adding calcium carbonate or sodium hydroxide during fermentation. However, Bacillus coagulans 2-6 can produce more than 180 g/L L-lactic acid when calcium lactate is accumulated, but less than 120 g/L L-lactic acid when sodium lactate is formed. The molecular mechanisms by which B. coagulans responds to calcium lactate and sodium lactate remain unclear. In this study, comparative transcriptomic methods based on high-throughput RNA sequencing were applied to study gene expression changes in B. coagulans 2-6 cultured in non-stress, sodium lactate stress and calcium lactate stress conditions. Gene expression profiling identified 712 and 1213 significantly regulated genes in response to calcium lactate stress and sodium lactate stress, respectively. Gene ontology assignments of the differentially expressed genes were performed. KEGG pathway enrichment analysis revealed that ‘ATP-binding cassette transporters’ were significantly affected by calcium lactate stress, and ‘amino sugar and nucleotide sugar metabolism’ was significantly affected by sodium lactate stress. It was also found that lactate fermentation was less affected by calcium lactate stress than by sodium lactate stress. Sodium lactate stress had negative effect on the expression of ‘glycolysis/gluconeogenesis’ genes but positive effect on the expression of ‘citrate cycle (TCA cycle)’ genes. However, calcium lactate stress had positive influence on the expression of ‘glycolysis/gluconeogenesis’ genes and had minor influence on ‘citrate cycle (TCA cycle)’ genes. Thus, our findings offer new insights into the responses of B. coagulans to different lactate stresses. Notably, our RNA-seq dataset constitute a robust database for investigating the functions of genes induced by lactate stress in the future and identify potential targets for genetic engineering to further improve L-lactic acid production by B. coagulans.

Genomic and Transcriptomic Insights into Calcium Carbonate Biomineralization by Marine Actinobacterium Brevibacterium linens BS258

“…RNA integrity was assessed using the RNA Nano6000 Assay Kit of the Bioanalyzer 2100 system (Agilent Technologies, Santa Clara, CA, USA). 16S rDNA was used as an internal reference and the relative gene expression was calculated using the 2 -ΔΔCt method (Qin et al, 2015). Specific primers for CAs and 16S rDNA were designed using Primer 6.0 as shown in Supplementary Table S1.…”

“…Then the total RNAs were reversely transcribed into cDNA and the transcriptional levels of 5 selected genes were determined by qRT-PCR using Sybr Green Premix Low rox (MDbio, China) and the QuantStudio 6 Flex (Thermo Fisher Scientific, America). 16S rDNA was used as an internal reference and the relative gene expression was calculated using the 2 -ΔΔCt method (Qin et al, 2015). Specific primers were designed using Primer 6.0 as shown in Supplementary Table S3.…”

Enhanced ε-Poly-L-Lysine Production by the Synergistic Effect of ε-Poly-L-Lysine Synthetase Overexpression and Citrate in Streptomyces albulus

“…The genes and primers used for qRT-PCR are shown in Supplementary Table S2. The relative gene expression data were analyzed using the 2 − Ct method, as described by Qin et al (2015). All qRT-PCR runs were conducted with three biological and three technical replicates.…”

Comparison of high-titer lactic acid fermentation from NaOH- and NH3-H2O2-pretreated corncob by Bacillus coagulans using simultaneous saccharification and fermentation

“…1B). These results demonstrate that during the initial stage of fermentation with a lower LA titer, LA was produced more rapidly when NaOH was used as the neutralizer; however, with increasing amounts of LA, soluble sodium lactate had a stronger inhibitory effect on B. coagulans than calcium lactate, which has been previously examined at the transcriptome level18. Finally, a significantly higher amount of LA (0.91 g/g vs. 0.79 g/g corncob) was produced from 8% NaOH-pretreated and washed corncob using CaCO 3 as the neutralizer compared to using NaOH as the neutralizer, as demonstrated by independent samples t-test ( p  < 0.05).…”

“…Moreover, calcium carbonate (CaCO 3 ) or NaOH are required to maintain the neutral or mildly acidic conditions favorable for LA fermentation. The resulting accumulation of sodium lactate or calcium lactate in the fermentation broth can have various stress effects on lactic acid bacteria18, however, like in other fermentation systems, removal of toxic products would improve fermentation yields19. Recently, several lactic acid bacteria, including Lactobacillus strains and Bacillus coagulans , have been reported to produce high-titer LA from lignocellulosic materials.…”