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Access type: UnknownSubject: search.filters.subject.Bacillus coagulans

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    Arthrospira Cell Residues for Lactic Acid Fermentation as Bioproducts From Waste Utilization
    (2022-06-13)
    Pan-utai, Wanida
    ;
    Thitiprasert, Sitanan
    ;
    Pornpukdeewattana, Soisuda
    Arthrospira (Spirulina) platensis is a freshwater cyanobacterium that is commercially produced as a food source on a global scale and considered safe for human consumption. After C-phycocyanin (C-PC) extraction, the waste cell residue (WCR) is composed of nutrients with 30% protein content. Here, the potential of WCR as a nitrogen source for Bacillus coagulans cultivation and bioproducts was evaluated. Nitrogen substitute from WCR under different conditions of 20—100 g L<sup>−1</sup> was performed. B. coagulans cultivation was achieved with maximal viable cells at 7.6–9.5 log CFU mL<sup>−1</sup>. Increasing WCR gave decreasing lactate production. The highest lactate production at 27 g L<sup>−1</sup> was achieved from WCR 20 g L<sup>−1</sup>, highlighting the potential use of A. platensis waste biomass residue as a nitrogen source for the growth of lactic acid bacteria and zero-waste biotechnology methodology. The utilization of renewable resources is a crucial step toward developing a sustainable industrial society.
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    Non-sterilized fermentation of high optically pure d-lactic acid by a genetically modified thermophilic Bacillus coagulans strain
    (2017-11-25)
    Zhang, Caili
    ;
    Zhou, Cheng
    ;
    Assavasirijinda, Nilnate
    ;
    Yu, Bo
    ;
    Wang, Limin
    Background: Optically pure d-lactic acid (≥99%) is an important precursor of polylactic acid. However, there are relatively few studies on d-lactic acid fermentation compared with the extensive investigation of l-lactic acid production. Most lactic acid producers are mesophilic organisms. Optically pure d-lactic acid produced at high temperature not only could reduce the costs of sterilization but also could inhibit the growth of other bacteria, such as l-lactic acid producers. Results: Thermophilic Bacillus coagulans is an excellent producer of l-lactic acid with capable of growing at 50°C. In our previous study, the roles of two l-lactic acid dehydrogenases have been demonstrated in B. coagulans DSM1. In this study, the function of another annotated possible l-lactate dehydrogenase gene (ldhL3) was verified to be leucine dehydrogenase with an activity of 0.16 units (μmol/min) per mg protein. Furthermore, the activity of native d-lactate dehydrogenase was too low to support efficient d-lactic acid production, even under the control of strong promoter. Finally, an engineered B. coagulans D-DSM1 strain with the capacity for efficient production of d-lactic acid was constructed by deletion of two l-lactate dehydrogenases genes (ldhL1 and ldhL2) and insertion of the d-lactate dehydrogenase gene (LdldhD) from Lactobacillus delbrueckii subsp. bulgaricus DSM 20081 at the position of ldhL1. Conclusions: This genetically engineered strain produced only d-lactic acid under non-sterilized condition, and finally 145g/L of d-lactic acid was produced with an optical purity of 99.9% and a high yield of 0.98g/g. This is the highest optically pure d-lactic acid titer produced by a thermophilic strain.