Response surface methodology: An effective optimization strategy for enhanced production of nitrile hydratase (NHase) by Rhodococcus rhodochrous (RS-6)

Response surface methodology guided approach for optimization of protein isolate from Faba bean. Part 1/2

Ultrasound-assisted extraction (UAE) was evaluated as a green procedure to produce faba beans protein isolates from faba beans. Magnetic stirring was performed as conventional extraction. A three-level five-factor Box-Behnken Design (BBD) was applied to obtain the optimal UAE conditions to concurrently maximize extraction yield and protein content. The response surface methodology (RSM) showed a quadratic curvature for extraction yield and protein. The optimal extraction conditions were determined as: Power of 123 W, solute/solvent ratio of 0.06 (1:15 g/mL), sonication time of 41 min, and total volume of 623 mL with a desirability value of 0.82. Under these conditions, the extraction yield of 19. 75 ± 0.87 % (Protein yield of 67.84 %) and protein content of 92.87 ± 0.53 % were obtained for optimum ultrasound extraction. Control samples using magnetic stirring under similar conditions without ultrasound treatment showed an extraction yield of 16.41 ± 0.02 % (Protein yield of 54.65 %) and a protein content of 89. 88 ± 0.40 %. This shows that BBD can effectively be used to optimize the extraction of proteins from faba beans using optimal extraction conditions, resulting in a higher extraction yield and protein purity.

Bioinformatics Analysis of the Genome of Rhodococcus rhodochrous IEGM 1362, an (-)-Isopulegol Biotransformer

A genome of Rhodococcus rhodochrous IEGM 1362 was sequenced and annotated. This strain can transform monoterpene alcohol (-)-isopulegol with the formation of two novel pharmacologically promising metabolites. Nine genes encoding cytochrome P450, presumably involved in (-)-isopulegol transformation, were found in the genome of R. rhodochrous IEGM 1362. Primers and PCR conditions for their detection were selected. The obtained data can be used for the further investigation of genes encoding enzymes involved in monoterpene biotransformation.

Immobilizing white-rot fungi laccase: Toward bio-derived supports as a circular economy approach in organochlorine removal

Despite their high persistence in the environment, organochlorines (OC) are widely used in the pharmaceutical industry, in plastics, and in the manufacture of pesticides, among other applications. These compounds and the byproducts of their decomposition deserve attention and efficient proposals for their treatment. Among sustainable alternatives, the use of ligninolytic enzymes (LEs) from fungi stands out, as these molecules can catalyze the transformation of a wide range of pollutants. Among LEs, laccases (Lac) are known for their efficiency as biocatalysts in the conversion of organic pollutants. Their application in biotechnological processes is possible, but the enzymes are often unstable and difficult to recover after use, driving up costs. Immobilization of enzymes on a matrix (support or solid carrier) allows recovery and stabilization of this catalytic capacity. Agricultural residual biomass is a passive environmental asset. Although underestimated and still treated as an undesirable component, residual biomass can be used as a low-cost adsorbent and as a support for the immobilization of enzymes. In this review, the adsorption capacity and immobilization of fungal Lac on supports made from residual biomass, including compounds such as biochar, for the removal of OC compounds are analyzed and compared with the use of synthetic supports. A qualitative and quantitative comparison of the reported results was made. In this context, the use of peanut shells is highlighted in view of the increasing peanut production worldwide. The linkage of methods with circular economy approaches that can be applied in practice is discussed.

Optimization of Rhodococcus erythropolis JCM3201T Nutrient Media to Improve Biomass, Lipid, and Carotenoid Yield Using Response Surface Methodology

The oleaginous bacterium Rhodococcus erythropolis JCM3201T offers various unique enzyme capabilities, and it is a potential producer of industrially relevant compounds, such as triacylglycerol and carotenoids. To develop this strain into an efficient production platform, the characterization of the strain's nutritional requirement is necessary. In this work, we investigate its substrate adaptability. Therefore, the strain was cultivated using nine nitrogen and eight carbon sources at a carbon (16 g L-1) and nitrogen (0.16 g L-1) weight ratio of 100:1. The highest biomass accumulation (3.1 ± 0.14 g L-1) was achieved using glucose and ammonium acetate. The highest lipid yield (156.7 ± 23.0 mg g-1DCW) was achieved using glucose and yeast extract after 192 h. In order to enhance the dependent variables: biomass, lipid and carotenoid accumulation after 192 h, for the first time, a central composite design was employed to determine optimal nitrogen and carbon concentrations. Nine different concentrations were tested. The center point was tested in five biological replicates, while all other concentrations were tested in duplicates. While the highest biomass (8.00 ± 0.27 g L-1) was reached at C:N of 18.87 (11 g L-1 carbon, 0.583 g L-1 nitrogen), the highest lipid yield (100.5 ± 4.3 mg g-1DCW) was determined using a medium with 11 g L-1 of carbon and only 0.017 g L-1 of nitrogen. The highest carotenoid yield (0.021 ± 0.001 Abs454nm mg-1DCW) was achieved at a C:N of 12 (6 g L-1 carbon, 0.5 g L-1 nitrogen). The presented results provide new insights into the physiology of R. erythropolis under variable nutritional states, enabling the selection of an optimized media composition for the production of valuable oleochemicals or pigments, such as rare odd-chain fatty acids and monocyclic carotenoids.

Optimization of Extraction Parameters and Characterization of Tunisian Date Extract: A Scientific Approach Toward Their Utilization

The response surface methodology (RSM) was used in order to select the extraction conditions of extract from Kentichi date powder; a by-product of the date-processing process. Powder/solvent ratio, extraction temperature, and extraction time all had an impact on sugar yield, and these model factors have quadratic effects influencing sugar yield. Optimal extraction was obtained with 300 g/L powder/solvent ratio, 32.7 °C extraction temperature, and 2.1 h extraction time. Under these conditions, Kentichi date powder's (KDP) sugar yield was 77.1%, which was close to the predicted value of the model (80.50%). The results of Kentichi date powder extract (KDPE) showed that the total sugar content is 160.09 g/L. However, the protein content is 10.31 g/L with a majority of the essential amino acids (essentially glutamic acid (28.39 mg/L) and aspartic acid (9.65 mg/L)). The determination of antioxidant activity of KDPE showed a high activity (DPPH IC₅₀ = 4.8 mg/mL, ABTS IC₅₀ = 3 mg/mL, FRAP = 4.70 μmol AAE/mL and, TAA = 18.04 μmol Fe(II)/mL). The results show also that the freeze-drying technique has a lot of potential for producing powder from KDPE with many desirable properties. The findings indicate that KDPE with a high nutritional value could be used as a component for the formulation of functional foods.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12355-022-01223-2.

A new source of bacterial myrosinase isolated from endophytic Bacillus sp. NGB-B10, and its relevance in biological control activity

Plant metabolism interacts strongly with the plant microbiome. Glucosinolates, secondary metabolites synthesized by Brassica plants, are hydrolyzed by myrosinase into bioactive compounds of great importance in human health and plant protection. Compared with myrosinase from plant sources, myrosinase enzymes of microbial origin have not been extensively investigated. Therefore, seven endophytic strains corresponding to Bacillus sp. were isolated from Eruca vesicaria ssp. sativa plants that could hydrolyse glucosinolates (sinigrin) in the culture medium and showed myrosinase activity (0.08–19.92 U mL⁻¹). The bglA myrosinase-related gene encoding the 6-phospho-β-glucosidase (GH 1) from Bacillus sp. NGB-B10, the most active myrosinase-producing bacterium, was successfully identified. Response surface methodology (RSM) was applied to statistically optimize culture conditions for myrosinase production from Bacillus sp. strain NGB-B10. The Plackett–Burman design indicated that nitrogen concentration, incubation period, and agitation speed were the significant parameters in myrosinase production. The application of the Box–Behnken design of RSM resulted in a 10.03-fold increase in enzyme activity as compared to the non-optimized culture conditions. The myrosinase was partially purified by 40% fractionation followed by SDS-PAGE analysis which yielded two subunits that had a molecular weight of 38.6 and 35.0 KDa. The purified enzyme was stable under a broad range of pH (5.5–10) and temperatures (10–65 °C). The hydrolysis products released by bacterial myrosinase from some glucosinolate extracts had higher and/or equivalent in vitro antagonistic activity against several phytopathogenic fungi compared to the nystatin (a broad-spectrum antifungal agent). This study provides original information about a new source of bacterial myrosinase and affords an optimized method to enhance myrosinase production.

Prospective Evaluation of an Amide-Based Zinc Scaffold as an Anti-Alzheimer Agent: In Vitro, In Vivo, and Computational Studies

Alzheimer's disease is the most common progressive neurodegenerative mental disorder associated with loss of memory, decline in cognitive function, and dysfunction of language. The prominent pathogenic causes of this disease involve deposition of amyloid-β plaques, acetylcholine neurotransmitter deficiency, and accumulation of neurofibrillary tangles. There are multiple pathways that have been targeted to treat this disease. The inhibition of the intracellular cyclic AMP regulator phosphodiesterase IV causes the increase in CAMP levels that play an important role in the memory formation process. Organometallic chemistry works in a different way in treating pharmacological disorders. In the field of medicinal chemistry and pharmaceuticals, zinc-based amide carboxylates have been shown to be a preferred pharmacophore. The purpose of this research work was to investigate the potential of zinc amide carboxylates in inhibition of phosphodiesterase IV for the Alzheimer's disease management. Swiss Albino mice under controlled conditions were divided into seven groups with 10 mice each. Group I was injected with carboxymethylcellulose (CMC) at 1 mL/100 g dose, group II was injected with Streptozotocin (STZ) at 3 mg/kg dose, group III was injected with Piracetam acting as a standard drug at 200 mg/kg dosage, while groups IV-VII were injected with a zinc scaffold at the dose regimen of 10, 20, 40, and 80 mg/kg through intraperitoneal injection. All groups except group I were injected with Streptozotocin on the first day and third day of treatment at the dose of 3 mg/kg through an intracerebroventricular route to induce Alzheimer's disease. Afterward, respective treatment was continued for all groups for 23 days. In between the treatment regimen, groups were analyzed for memory and learning improvement through various behavioral tests such as open field, elevated plus maze, Morris water maze, and passive avoidance tests. At the end of the study, different biochemical markers in the brain were estimated like neurotransmitters (dopamine, serotonin and adrenaline), oxidative stress markers (superoxide dismutase, glutathione, and catalase), acetylcholinesterase (AchE), tau proteins, and amyloid-β levels. A PCR study was also performed. Results showed that the LD₅₀ of the zinc scaffold is greater than 2000 mg/kg. Research indicated that the zinc scaffold has the potential to improve the memory impairment and learning behavior in Alzheimer's disease animal models in a dose-dependent manner. At the dose of 80 mg/kg, a maximum response was observed for the zinc scaffold. Maximum reduction in the acetylcholinesterase enzyme was observed at 80 mg/kg dose, which was further strengthened and verified by the PCR study. Oxidative stress was restored by the zinc scaffold due to the significant activation of the endogenous antioxidant enzymes. This research ended up with the conclusion that the zinc-based amide carboxylate scaffold has the potential to improve behavioral disturbances and vary the biochemical markers in the brain.

High-throughput screening for distinguishing nitrilases from nitrile hydratases in Aspergillus and application of a Box-Behnken design for the optimization of nitrilase

Nitrilases and nitrile hydratases/amidases hydrolyze nitriles into carboxylic acids and/or amides, which are used in industrial chemical processes. In the present study, 26 microorganisms, including yeasts and filamentous fungi, in a minimum solid mineral medium supplemented with glucose and phenylacetonitrile were screened to evaluate their biocatalytic potential. Of these microorganisms, five fungi of the genus Aspergillus were selected and subjected to colorimetry studies to evaluate the production and distinction of nitrilase and nitrile hydratase/amidase enzymes. Aspergillus parasiticus Speare 7967 and A. niger Tiegh. 8285 produced nitrilases and nitrile hydratase, respectively. Nitrilase optimization was performed using a Box-Behnken design (BBD) and fungus A. parasiticus Speare 7967 with phenylacetonitrile volume (μl), pH, and carbohydrate source (starch:glucose; g/g) as independent variables and nitrilase activity (U ml^-1 ) as dependent variable. Maximum activity (2.97 × 10^-3  U ml^-1 ) was obtained at pH 5.5, 80 μl of phenylacetonitrile, and 15 g of glucose. A. parasiticus Speare 7967 showed promise in the biotransformation of nitriles to carboxylic acids.

Evaluation of acrylamide production by Rhodococcus rhodochrous (RS-6) cells immobilized in agar matrix

AIMS

The efficiency of acrylamide production was examined with immobilized cells of Rhodococcus rhodochrous (RS-6) containing NHase.

METHODS AND RESULTS

Different entrapment matrices such as agar, alginate and polyacrylamide were used. Various immobilization parameters like agar concentration, cell concentration and reaction conditions affecting the bioconversion process using suitable matrices were determined. The cells immobilized with agar matrix were found to be most effective for acrylonitrile conversion. The bioconversion was more efficient in beads prepared with 2% agar and 5% (v/v) cell concentration. The entire conversion of acrylonitrile to acrylamide with agar entrapped cells was achieved in 120 min at 15°C. The agar entrapped R. rhodochrous (RS-6) cells exhibited 8% (w/v) tolerance to acrylonitrile and 35% tolerance to acrylamide. The immobilized cells also retained 50% of its conversion ability up to seven cycles. The laboratory-scale (1 L) production resulted in 466 g L^-1 accumulation of acrylamide in 16 h.

CONCLUSIONS

The cells immobilized in agar showed better stability and biocatalytic properties and increased reusability potential.

SIGNIFICANCE AND IMPACT OF THE STUDY

The agar-immobilized Rhodococcus rhodochrous (RS-6) cells showed enhanced tolerance for both the substrate and product and is economical for the large-scale production of acrylamide.

Engineering interventions in enzyme production: Lab to industrial scale

Commercial enzyme production has gained popularity due to its extensive applications in traditional and modern industrial sectors. Rigorous research activities are being conducted worldwide to make the enzyme production system more efficient, cost-effective and hence, sustainable. To overcome the lacunae in earlier enzyme production methods, new engineering interventions are being introduced to meet the growing demand for industrial enzymes. This review focuses initially on the current global scenario of the enzyme market followed by a discussion on different bioreactor design approaches. The use of novel membrane based, airlift and reciprocating plate bioreactors along with the emergence of micro-reactors have also been discussed. Further, the review covers different modelling and optimization strategies for the enzyme production process including advanced techniques like neural networks, adaptive neuro-fuzzy inference systems and genetic algorithms. Finally, the required thrust areas in the enzyme production sector have been highlighted with directions for future research.