Whole cell immobilisation of Natrinema gari BCC 24369 for histamine degradation

Biodegradation of bisphenol A by a Pichia pastoris whole-cell biocatalyst with overexpression of laccase from Bacillus pumilus and investigation of its potential degradation pathways

Bisphenol A (BPA), an endocrine disrupter with estrogen activity, can infiltrate animal and human bodies through the food chain. Enzymatic degradation of BPA holds promise as an environmentally friendly approach while it is limited due to lower stability and recycling challenges. In this study, laccase from Bacillus pumilus TCCC 11568 was expressed in Pichia pastoris (fLAC). The optimal catalytic conditions for fLAC were at pH 6.0 and 80 °C, with a half-life T1/2 of 120 min at 70 °C. fLAC achieved a 46 % degradation rate of BPA, and possible degradation pathways were proposed based on identified products and reported intermediates of BPA degradation. To improve its stability and degradation capacity, a whole-cell biocatalyst (WCB) was developed by displaying LAC (dLAC) on the surface of P. pastoris GS115. The functionally displayed LAC demonstrated enhanced thermostability and pH stability along with an improved BPA degradation ability, achieving a 91 % degradation rate. Additionally, dLAC maintained a degradation rate of over 50 % after the fourth successive cycles. This work provides a powerful catalyst for degrading BPA, which might decontaminate endocrine disruptor-contaminated water through nine possible pathways.

Histamine-degrading halophilic bacteria from traditional fish sauce: Characterization of Virgibacillus campisalis TT8.5 for histamine reduction

Traditionally produced fish sauce can contain significant amounts of histamine. In some instances, the histamine concentration may be well above the limit recommended by the Codex Alimentarius Commission. The aim of this study was to discover new bacterial strains capable of growing under the stressful environmental conditions of fish sauce fermentation and metabolizing histamine. In this study, 28 bacterial strains were isolated from Vietnamese fish sauce products based on their ability to grow at high salt concentrations (23% NaCl) and tested for their ability to degrade histamine. Strain TT8.5 showed the highest histamine-degradation (45.1 ± 0.2% of initially 5 mM histamine within 7 days) and was identified as Virgibacillus campisalis TT8.5. Its histamine-degrading activity was shown to be localized intracellularly and the enzyme is a putative histamine dehydrogenase. The strain exhibited optimal growth and histamine-degrading activity at 37°C, pH 7%, and 5% NaCl in halophilic archaea (HA) histamine broth. It also showed pronounced histamine-degrading activity in HA histamine broth when cultivated at temperatures of up to 40 °C as well as in the presence of up to 23% NaCl. After treatment with immobilized cells, 17.6-26.9% of the initial histamine in various fish sauce products were reduced within 24 h of incubation, while no significant changes in other parameters of fish sauce quality were observed after this treatment. Our results indicate that V. campisalis TT8.5 is of potential interest to be applied in histamine degradation of traditional fish sauce.

Utilization of Soybean Oil Waste for a High-Level Production of Ceramide by a Novel Phospholipase C as an Environmentally Friendly Process

Ceramide is a natural functional ingredient as food additive and medicine that has attracted extensive attention in the food, medical, and cosmetic industries. Here, we developed a biotechnological strategy based on a recombinant whole-cell biocatalyst for efficiently producing ceramide from crude soybean oil sediment (CSOS) waste. A novel phospholipase C (PLC_ac) from Acinetobacter calcoaceticus isolated from soil samples was identified and characterized. Furthermore, recombinant Komagataella phaffii displaying PLC_ac (dPLC_ac) on the cell surface was constructed as a whole-cell biocatalyst with better thermostability (30-60 °C) and pH stability (8.0-10.0) to successfully produce ceramide. After synergistical optimization of reaction time and dPLC_ac dose, the ceramide yield of hydrolyzing from CSOS using dPLC_ac was 51% (the theoretical maximum yield of converting sphingomyelin, ∼70%) and the relative yield was over 50% after seven consecutive 4 h batches under the optimized conditions. Our study provides a potentially promising strategy for the commercial production of ceramide.

New insights into halophilic prokaryotes isolated from salting-ripening anchovies (Engraulis anchoita) process focused on histamine-degrading strains

Salted and ripened fish foods are susceptible to cause histamine poisoning. The present study focuses on microbial histamine degradation from high salted fermented fishery products to deepen our understanding about this new and growing field of research. As a result of this first study related to salted-ripened anchovies (Engraulis anchoita), fifty seven moderate and extreme halophilic microbial isolates from salt and salted-ripened anchovy processes were characterized in terms of their phenotype and histamine-degrading capacity. Only 7%-4 isolates-were able to degrade histamine. None of the histamine-degrading isolates presented proteolytic and/or lipolytic activity. One of them designated A18 was chemotactic toward histamine, an interesting property not previously reported for that chemoattractant. However, the S18 and A18 isolates, genotypically identified as Halobacterium sp. and Halomonas sp. respectively, produced indole and/or H₂S, both undesirable characteristics associated to off-flavors occurrence. On the other hand, A28 and S20, identified as Halovibrio sp. and Halobacterium sp. respectively, presented desirable properties, such as cytochrome oxidase and catalase activity, and non-production of H₂S and indole. These strains also showed characteristics previously reported as dominant in the ripened stage. The results are promising, and A28 and S20 may have the desirable features to improve the anchovy salting-ripening process.

Preliminary Study on the Determination of ppm-Level Concentration of Histamine in Tuna Fish Using a Dry Extract System for Infrared Coupled with Near-Infrared Spectroscopy

Rapid and simple methods to determine histamine in tuna fish have been examined. A dry extract system for infrared (DESIR) was coupled with near-infrared spectroscopy in order to obtain the absorption of histamine in tuna fish at the ppm level. The result showed that the optimal extraction solvent for preparing DESIR samples was 75% methanol and boiling water (100 °C). Calibration equations were developed and tested by independent validation set samples. The calibration equation developed from boiling water as solvent extraction was slightly better than the equation developed from 75% methanol solvent with a coefficient of determination (R 2) of 0.79, a standard error of calibration of 2.45 ppm, a standard error of prediction of 2.94 ppm, and a bias of 0.10 ppm. Furthermore, the predicted values from both equations were not significantly different from the reference values obtained from the standard method at the 95% confidence interval. Compared to the current AOAC fluorometric official method, the proposed technique simplified and reduced the preparation time.

Advanced Rhodococcus Biocatalysts for Environmental Biotechnologies

The review is devoted to biocatalysts based on actinobacteria of the genus Rhodococcus, which are promising for environmental biotechnologies. In the review, biotechnological advantages of Rhodococcus bacteria are evaluated, approaches used to develop robust and efficient biocatalysts are discussed, and their relevant applications are given. We focus on Rhodococcus cell immobilization in detail (methods of immobilization, criteria for strains and carriers, and optimization of process parameters) as the most efficient approach for stabilizing biocatalysts. It is shown that advanced Rhodococcus biocatalysts with improved working characteristics, enhanced stress tolerance, high catalytic activities, human and environment friendly, and commercially viable are developed, which are suitable for wastewater treatment, bioremediation, and biofuel production.

Significantly enhanced substrate tolerance of Pseudomonas putida nitrilase via atmospheric and room temperature plasma and cell immobilization

The objective of the study was to enhance the substrate tolerance of Pseudomonas putida nitrilase via atmospheric and room temperature plasma (ARTP) and cell immobilization. The mutant library was constructed by ARTP and rapidly screened by an OPA-TCA microscale reaction. A mutant strain of mut-D3 was obtained and its optimum substrate concentration was improved to 150mM from 100mM. It could accumulate 189g/L nicotinic acid (NA) from 3-cyanopyridine (3-CP), which was increased by 42% compared with that of wild type (WT). Additionally, composite immobilization of mut-D3 was performed and SA-PVA immobilized cells could catalyze 250mM 3-CP each batch with finally accumulating 346g/L NA, while free cells accumulated 175g/L NA. These results indicated that the free or immobilized catalysts of mut-D3 could serve as a good choice for NA production. This is the first report on mutation breeding of nitrilase-producing microorganisms by ARTP.

Degradation of Histamine by Lactobacillus plantarum Isolated from Miso Products

Histamine is a toxic chemical and is the causative agent of food poisoning. This foodborne toxin may be degraded by the oxidative deamination activity of certain microorganisms. In this study, we isolated four histamine-degrading Lactobacillus plantarum bacteria from miso products. Among them, L. plantarum D-103 exhibited 100% degradation of histamine in de Man Rogosa Sharpe (MRS) broth containing 50 ppm of histamine after 24 h of incubation at 30°C. The optimal growth, histamine oxidase, and histamine-degrading activity of L. plantarum D-103 were observed in histamine MRS broth at pH 7.0, 3% NaCl, and 30°C. It also exhibited tolerance to broad ranges of pH (4 to 10) and salt concentrations (0 to 12%) in histamine MRS broth. Therefore, the histamine-degrading L. plantarum D-103 might be used as an additive culture to prevent histamine accumulation in miso products during fermentation.

Systematics of haloarchaea and biotechnological potential of their hydrolytic enzymes

Halophilic archaea, also referred to as haloarchaea, dominate hypersaline environments. To survive under such extreme conditions, haloarchaea and their enzymes have evolved to function optimally in environments with high salt concentrations and, sometimes, with extreme pH and temperatures. These features make haloarchaea attractive sources of a wide variety of biotechnological products, such as hydrolytic enzymes, with numerous potential applications in biotechnology. The unique trait of haloarchaeal enzymes, haloenzymes, to sustain activity under hypersaline conditions has extended the range of already-available biocatalysts and industrial processes in which high salt concentrations inhibit the activity of regular enzymes. In addition to their halostable properties, haloenzymes can also withstand other conditions such as extreme pH and temperature. In spite of these benefits, the industrial potential of these natural catalysts remains largely unexplored, with only a few characterized extracellular hydrolases. Because of the applied impact of haloarchaea and their specific ability to live in the presence of high salt concentrations, studies on their systematics have intensified in recent years, identifying many new genera and species. This review summarizes the current status of the haloarchaeal genera and species, and discusses the properties of haloenzymes and their potential industrial applications.

Enhanced production of histamine dehydrogenase by Natrinema gari BCC 24369 in a non-sterile condition

The production of histamine dehydrogenase (HADH) by Natrinema gari BCC 24369, a halophilic archeaon isolated from fish sauce, was optimized and scaled up under a non-sterile condition. Through statistical design by Plackett-Burman design (PBD), casamino acid, NaCl, MgSO4·7H2O and FeCl2·4H2O were identified as the significant medium compositions influencing HADH production. Central composite design (CCD) was employed to identify the optimal values of individual composition yielding the maximum HADH production. The analysis indicated that the optimal medium was composed of 15 g/l casamino acid, 75 g/l MgSO4·7H2O, 273 g/l NaCl, 2.5 mg/l FeCl2·4H2O, 10 g/l yeast extract, 5 g/l sodium glutamate and 5 g/l KCl. Based on the one-factor-at-a-time (OFAT) method, the optimum initial pH of the culture medium and the incubation temperature for HADH production were 7.5 and 37 °C, respectively. The production of HADH under optimal conditions was 2.2-fold higher than that under un-optimized conditions. Owing to the halophilic nature of Nnm. gari BCC 24369, a more economical and eco-friendlier HADH production was developed under a completely non-sterile condition. In a 16-l batch cultivation of Nnm. gari BCC 24369, HADH productivity under a non-sterile condition (858 ± 12 U/g cell biomass) was comparable to that under a sterile condition (878 ± 15 U/g cell biomass). These results demonstrate the feasibility and simplicity of HADH production using Nnm. gari BCC 24369 under a non-sterile condition without compromising enzyme yield and any changes in Km value.

Reduction of Biogenic Amines during Miso Fermentation by Lactobacillus plantarum as a Starter Culture

Lactobacillus plantarum D-103 isolated from a miso product that possesses amine-degrading activity was used as a starter culture in miso fermentation (25°C for 120 days) in this study. The salt content in control samples (without starter culture) and inoculated samples (inoculated with L. plantarum D-103) remained constant at 10.4% of the original salt concentration throughout fermentation, whereas the pH value decreased from 6.2 to 4.6 during fermentation. The inoculated samples had significantly lower (P < 0.05) levels of total volatile basic nitrogen than control samples after 40 days of fermentation. After 120 days of fermentation, the histamine and overall biogenic amine contents in inoculated samples were reduced by 58 and 27%, respectively, compared with control samples. To our knowledge, this is the first report to demonstrate that application of a starter culture with amine-degrading activity in miso products was effective in reducing the accumulation of biogenic amines.

Reduction of histamine and biogenic amines during salted fish fermentation by Bacillus polymyxa as a starter culture

Bacillus polymyxa D05-1, isolated from salted fish product and possessing amine degrading activity, was used as a starter culture in salted fish fermentation in this study. Fermentation was held at 35°C for 120 days. The water activity in control samples (without starter culture) and inoculated samples (inoculated with B. polymyxa D05-1) remained constant throughout fermentation, whereas the pH value rose slightly during fermentation. Salt contents in both samples were constant in the range of 17.5–17.8% during the first 60 days of fermentation and thereafter increased slowly. The inoculated samples had considerably lower levels of total volatile basic nitrogen (p < 0.05) than control samples at each sampling time during 120 days of fermentation. Aerobic bacterial counts in inoculated samples were retarded during the first 60 days of fermentation and thereafter increased slowly, whereas those of control samples increased rapidly with increased fermentation time. However, the aerobic bacterial counts of control samples were significantly higher (p < 0.05) than those of inoculated samples after 40 days of fermentation. In general, overall biogenic amine contents (including histamine, putrescine, cadaverine, and tyramine) in the control samples were markedly higher (p < 0.05) than those of the inoculated samples throughout fermentation. After 120 days of fermentation, the histamine and overall biogenic amine contents in the inoculated samples were reduced by 34.0% and 30.0%, respectively, compared to control samples. These results emphasize that the application of starter culture with amines degrading activity in salted fish products was effective in reducing biogenic amine accumulation.

Degradation of histamine by Bacillus polymyxa isolated from salted fish products

Histamine is the causative agent of scombroid poisoning, a foodborne chemical hazard. Histamine is degraded by the oxidative deamination activity of certain microorganisms. In this study, eight histamine-degrading bacteria isolated from salted fish products were identified as Rummeliibacillus stabekisii (1 isolate), Agrobacterium tumefaciens (1 isolate), Bacillus cereus (2 isolates), Bacillus polymyxa (1 isolate), Bacillus licheniformis (1 isolate), Bacillus amyloliquefaciens (1 isolate), and Bacillus subtilis (1 isolate). Among them, B. polymyxa exhibited the highest activity in degrading histamine than the other isolates. The ranges of temperature, pH, and salt concentration for growth and histamine degradation of B. polymyxa were 25–37°C, pH 5–9, and 0.5–5% NaCl, respectively. B. polymyxa exhibited optimal growth and histamine-degrading activity at 30°C, pH 7, and 0.5% NaCl in histamine broth for 24 hours of incubation. The histamine-degrading isolate, B. polymyxa, might be used as a starter culture in inhibiting histamine accumulation during salted fish product fermentation.

Production of biosurfactant on crude date syrup under saline conditions by entrapped cells of Natrialba sp. strain E21, an extremely halophilic bacterium isolated from a solar saltern (Ain Salah, Algeria)

A bacterial strain E21 was isolated from a sample of water collected in the salt lake located close to Ain Salah, Algeria. The analysis of 16S rRNA gene sequence had indicated that the strain had 93 % sequence similarity with the genus Natrialba sp. strain E21 (GenBank, FR750525.1) and was considered extremely halophilic. Production of biosurfactant by the strain E21 with free and entrapped cells was investigated using soluble starch in the saline conditions. Biosurfactant synthesis was followed by measuring the surface tension and emulsifying index 9 days under optimal conditions (40 °C, pH 7). Some diffusional limitations in alginate and agar beads affected the kinetics of biosurfactant production when compared to that obtained with free cells culture. The minimum values of surface tension were 27 and 30 mN m(-1) achieved after 9 days with free and immobilized cells, respectively, while the corresponding maximum E24 values were 65.3 and 62.3 %, respectively. The re-use of bacterial cells along with the limited cell losses provided by the immobilized system might lead to significant reduction of the biosurfactant production cost.

Could halophilic archaea improve the traditional salted anchovies (Engraulis encrasicholus L.) safety and quality?

AIMS

The positive influence of two selected extremely halophilic archaea strains in the production of salted anchovies (Engraulis encrasicolus, L., 1758) was highlighted.

METHODS AND RESULTS

Anchovies produced with salt artificially contaminated with halophiles exhibited lower loads of staphylococci, Enterobacteriaceae and lactic acid bacteria, and a reduced content of histamine as well as an improved organoleptic acceptance.

CONCLUSIONS

The findings of this survey are expected to enhance the safety of salted anchovies, with regard to the histamine formation during ripening, and to improve the sensory attributes of this product.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study represents the first report on the positive influence of halophilic archaea in traditional salted anchovies production, thus suggesting new perspectives about a conscious employment of properly selected haloarchaea strains in this traditional manufacture.