Assessment of Relevant Factors Influencing Lipolytic Enzyme Production by Thermus thermophilus HB27 in Laboratory-Scale Bioreactors

Effect of process parameters and surfactant additives on the obtained activity of recombinant tryptophan hydroxylase (TPH1) for enzymatic synthesis of 5-hydroxytryptophan (5-HTP)

5-hydroxytryptophan (5-HTP) is an intermediate molecule in the biosynthesis of serotonin, an important neurotransmitter, regulating a series of metabolic and psychological functions in humans. In this work, we studied the heterologous production of Human tryptophan hydroxylase (TPH1) in Escherichia coli, for the synthesis of 5-hydroxytryptophan (5-HTP) from Tryptophan (Trp). To quantify TPH1 activity, a simple fluorescence-based microtiter plate assay was established, based on the changes in fluorescence emission at 340 nm between substrate and product when excited at 310 nm, allowing quick and reliable quantification of released 5-HTP. To increase enzyme production, heterologous TPH1 production was studied in stirred tank bioreactor scale. The effect of rate of aeration (0.25, 0.50 and 0.75 vvm) and agitation (150, 250 and 500 rpm) was evaluated for biomass production, pH, volumetric oxygen transfer coefficient (k_La) and volumetric TPH1 activity. We determined that high agitation and low aeration allowed reaching the maximum measured enzyme activity. Under such conditions, we observed a 90% substrate conversion, obtaining 90 µM (~0.02 g/L) 5-HTP from a 100 µM Tryptophan substrate solution. Finally, we observed that the addition of Tween 20 (0.1%) in the culture broth under production conditions expanded the pH operation range of TPH1. Our results establish a base for a biocatalytic approach as a potential alternative process for the synthesis of 5-HTP using recombinant TPH1.

Demonstrating the viability of halolipase production at a mechanically stirred tank biological reactor

The definition of halophiles as "the coming stars of industrial biotechnology" in a recent review demands new research efforts for their efficient production at bioreactor scale. In this sense, the scarcity of information about halolipases production has furthered the research on the viability of Halomonas sp. LM1C culture in a mechanically stirred bioreactor. The operating conditions have been optimized by means of a Central Composite Face-Centered (CCFC) design. The operation at low aerations (0.25 vvm) and moderate agitation rates (583 rpm) led to activity levels near 8000 U/L, which clearly surpasses the typical values detected for other extremophilic enzymes. The process at optimum conditions has been kinetically characterized and the oxygen volumetric mass transfer coefficient (K_La) has been determined.

Unravelling the suitability of biological induction for halophilic lipase production by Halomonas sp. LM1C cultures

In this study, the viability of using biological induction as an alternative to the conventional chemical induction in lipase production by a novel halophilic microorganism, Halomonas sp. LM1C, has been demonstrated. Thus, a 9-times increase of lipase activity (3000U/L) was recorded when Staphylococcus equorum sp. AMC7 was present in the medium, which is competitive with the results obtained when Triton X-100 was added as chemical inducer. The GC-MS data allowed concluding the true nature of the biological inducer effect, as the existence of high percentages of isomeric forms of pentadecanoic acid were detected. The suitability of the proposed strategy was validated by operating at bench scale bioreactor, and the influence of bioreactor configuration on the biomass and lipolytic activity levels was studied. All the data were fitted to logistic and Luedeking & Piret models to characterize the bioprocess kinetics, concluding the growth-associated character of the produced lipolytic enzymes.

Thermus thermophilus as a Source of Thermostable Lipolytic Enzymes

Lipolytic enzymes, esterases (EC 3.1.1.1) and lipases (EC 3.1.1.3), catalyze the hydrolysis of ester bonds between alcohols and carboxylic acids, and its formation in organic media. At present, they represent about 20% of commercialized enzymes for industrial use. Lipolytic enzymes from thermophilic microorganisms are preferred for industrial use to their mesophilic counterparts, mainly due to higher thermostability and resistance to several denaturing agents. However, the production at an industrial scale from the native organisms is technically complicated and expensive. The thermophilic bacterium Thermus thermophilus (T. thermophilus) has high levels of lipolytic activity, and its whole genome has been sequenced. One esterase from the T. thermophilus strain HB27 has been widely characterized, both in its native form and in recombinant forms, being expressed in mesophilic microorganisms. Other putative lipases/esterases annotated in the T. thermophilus genome have been explored and will also be reviewed in this paper.

Assessment of a process to degrade metal working fluids using Pseudomonas stutzeri CECT 930 and indigenous microbial consortia

The development of a novel biological process to treat metal working fluids (MWFs)-containing effluents at bioreactor scale was pursued in this work. The bacteria Pseudomonas stutzeri CECT 930 was investigated for the first time as an alternative agent for MWF degradation. An adequate medium design and mixing and aeration system, as well as an appropriate microorganism proved to be crucial for reaching high levels of degradation by P. stutzeri and by an indigenous consortium (about 70% and 50% of reduction in total petroleum hydrocarbon content in less than 2 wk, respectively). Additionally, as there is no information in literature trying to kinetically characterize an MWF-polluted effluent degradation process, all the experimental data were fitted to logistic and Luedeking and Piret models, that allowed to elucidate the growth-associated character of the biodegradation process.

Decolorization of dye Reactive Black 5 by newly isolated thermophilic microorganisms from geothermal sites in Galicia (Spain)

In this study, thermophilic microbial strains from thermal spots in northwestern Spain displaying excellent decolorization capability were isolated. The research work tackled: (i) the ability of consortia to degrade a model di-azo dye Reactive Black at different pHs in flask cultures, obtaining that just neutral pHs licensed degradation levels near to 70%, (ii) the isolation of tree of the bacteria, which rendered possible reaching high levels of decolorization (80%) after just 24 h in aerobic conditions, and which were identified through 16S rRNA sequencing to possess high homology (99%) with Anoxybacillus pushchinoensis, Anoxybacillus kamchatkensis and Anoxybacillus flavithermus, and (iii) the cultivation of the isolates in a bench-scale bioreactor, which led to a decolorization rate two-fold higher than that obtained in flask cultures. Therefore, this work makes up the first time that a decolorization process of an azo dye by thermophilic microorganisms in aerobic conditions is investigated.