Optimized medium via statistical approach enhanced threonine production by Pediococcus pentosaceus TL-3 isolated from Malaysian food

Abstract

Background: Threonine is an essential amino acid that is extensively used in livestock industry as feed supplement due to its pronounced effect in improving the growth performance of animals. Application of genetically engineered bacteria for amino acid production has its share of controversies after eosinophils myalgia syndrome outbreak in 1980s. This has urged for continuous search for a food grade producer as a safer alternative for industrial amino acid production. Lactic acid bacteria (LAB) appear as an exceptional candidate owing to their non-pathogenic nature and reputation of Generally Recognized as Safe (GRAS) status. Recently, we have identified a LAB, Pediococcus pentosaceus TL-3, isolated from Malaysian food as a potential threonine producer. Thus, the objective of this study was to enhance the threonine production by P. pentosaceus TL-3 via optimized medium developed by using Plackett-Burman design (PBD) and central composite design (CCD). Results: Molasses, meat extract, (NH 4) 2 SO 4 , and MnSO 4 were identified as the main medium components for threonine production by P. pentosaceus TL-3. The optimum concentration of molasses, meat extract, (NH 4) 2 SO 4 and MnSO 4 were found to be 30.79 g/L, 25.30 g/L, 8.59 g/L, and 0.098 g/L respectively based on model obtained in CCD with a predicted net threonine production of 123.07 mg/L. The net threonine production by P. pentosaceus TL-3 in the optimized medium was enhanced approximately 2 folds compared to the control. Conclusions: This study has revealed the potential of P. pentosaceus TL-3 as a safer alternative to produce threonine. Additionally, the current study has identified the key medium components affecting the production of threonine by P. pentosaceus TL-3, followed by optimization of their concentrations by means of statistical approach. The findings of this study could act as a guideline for the future exploration of amino acid production by LAB.

Rapid Evaluation and Optimization of Medium Components Governing Tryptophan Production by Pediococcus acidilactici TP-6 Isolated from Malaysian Food via Statistical Approaches

“…Ooi et al [59] also reported that yeast extract was crucial for bacteriocin production by L. plantarum I-UL4, whereby the bacteriocin production was only detected when yeast extract was present. Similar findings were reported by Lim et al [60], where all the organic nitrogen sources demonstrated a significant stimulatory effect (p < 0.05) on the growth of Pediococcus pentosaceus TL-3, highlighting the crucial role of organic nitrogen sources for the growth of P. pentosaceus TL-3. Unlike organic nitrogen sources, the effect of inorganic nitrogen sources on the growth of P. acidilactici TP-6 was less prominent, whereby only 2 out of the 4 studied inorganic nitrogen sources affected the cell growth of P. acidilactici TP-6 significantly (p < 0.05) with (NH4)2HC6H5O7 demonstrated a highly significant stimulatory effect (p < 0.01), whereas (NH4)2SO4 exerted a highly significant inhibitory effect (p < 0.01).…”

“…As a comparison, the vitamin biotin used in this study affected the growth of P. acidilactici TP-6 highly significantly (p < 0.01) in a negative manner. Similar effect was also observed for the growth of a threonine producer, P. pentosaceus TL-3, where biotin affected the growth of the isolate P. pentosaceus TL-3 significantly in a negative manner [60]. However, a contradictory finding was reported by Tripuraneni [69], where the inclusion of biotin in the growth medium of LAB enhanced the bacterial growth.…”

“…In contrast, the presence of phosphate ion could potentially lead to the elevation of pH, which in turn created an alkaline environment. As a consequence, the growth of acidophiles such as LAB could be retarded [60]. This could explain the inhibitory effect of KH 2 PO 4 and K 2 HPO 4 towards the growth of P. acidilactici TP-6.…”

“…The strain was cultivated and preserved as described by Kareem et al [73]. The inoculum preparation was performed as described by Lim et al [60].…”

“…The design of experiment and statistical analysis of data were performed by using Design Expert statistical software version 9.0.6.2 (State-Ease Inc, Minneapolis, MN, USA). A number of 22 medium components which might affect amino acid production were selected based on published reports and control MRS medium composition and evaluated in the current study by assigning each variable at two distinct levels, namely low level (−1) and high level (+1) as presented in Table 9 [60]. Table 10 presents matrixes of the PBD constituting of 24 experimental runs as suggested by the software.…”