Statistical Optimization of Phenol Degradation by Bacillus pumilus OS1 Using Plackett–Burman Design and Response Surface Methodology

Optimized phenol degradation and lipid production by Rhodosporidium toruloides using response surface methodology and genetic algorithm-optimized artificial neural network

Oleaginous yeast can produce lipids while degrading phenol in wastewater treatment. In this study, a Plackett-Burman Design (PBD) was adopted to identify key factors of phenol degradation and lipid production using R toruloides 9564T. While temperature, inoculum size, and agitation were significant for both the processes (p < 0.05), pH and incubation were significant for lipid production, and phenol removal, respectively. Results from four factors (pH, temperature, inoculum size, and incubation period) central composite design (CCD) experiment were used to formulate quadratic and genetic algorithm-optimized ANN models. The reduced quadratic model for phenol degradation (R2: 0.993) and lipid production (R2: 0.958) were marginally inferior to ANN models (R2: 0.999, 0.982, respectively) on training sets. Multi-objective optimization with equal importance suggests phenol degradation between 106.4 and 108.76%, and lipid production of 0.864-0.903 g/L, by polynomial and ANN models. Complete phenol degradation (100%) and 3.35-fold increment (0.918 g/L) in lipid production were obtained at pH 6.07, inoculum size 14.68% v/v, at 29.5 °C in 92.17 h experimentally.

Fabrication and Characterization of β-Cyclodextrin/Mosla Chinensis Essential Oil Inclusion Complexes: Experimental Design and Molecular Modeling

Essential oils (EOs) are primarily isolated from medicinal plants and possess various biological properties. However, their low water solubility and volatility substantially limit their application potential. Therefore, the aim of the current study was to improve the solubility and stability of the Mosla Chinensis (M. Chinensis) EO by forming an inclusion complex (IC) with β-cyclodextrin (β-CD). Furthermore, the IC formation process was investigated using experimental techniques and molecular modeling. The major components of M. Chinensis 'Jiangxiangru' EOs were carvacrol, thymol, o-cymene, and terpinene, and its IC with β-CD were prepared using the ultrasonication method. Multivariable optimization was studied using a Plackett-Burman design (step 1, identifying key parameters) followed by a central composite design for optimization of the parameters (step 2, optimizing the key parameters). SEM, FT-IR, TGA, and dissolution experiments were performed to analyze the physicochemical properties of the ICs. In addition, the interaction between EO and β-CD was further investigated using phase solubility, molecular docking, and molecular simulation studies. The results showed that the optimal encapsulation efficiency and loading capacity of EO in the ICs were 86.17% and 8.92%, respectively. Results of physicochemical properties were different after being encapsulated, indicating that the ICs had been successfully fabricated. Additionally, molecular docking and dynamics simulation showed that β-CD could encapsulate the EO component (carvacrol) via noncovalent interactions. In conclusion, a comprehensive methodology was developed for determining key parameters under multivariate conditions by utilizing two-step optimization experiments to obtain ICs of EO with β-CD. Furthermore, molecular modeling was used to study the mechanisms involved in molecular inclusion complexation.

Biodegradation modeling of phenol using Curtobacterium flaccumfaciens as plant-growth-promoting bacteria

Phenol is a major worry pollutant resulting from industrialized manufacturing and chemical reactions. The growth kinetics and biodegradation of phenol were initially investigated using C. flaccumfaciens, a recently identified plant growth stimulating bacterium. Based on the Haldane inhibition model, Haldane's growth kinetics inhibition coefficient (Ki), half-saturation coefficient (Ks), and the maximum specific growth rate (max) for phenol-dependent growth kinetics were estimated to be 329 (mg/L), 9.14 (mg/L), and 1.05 (h-1), respectively. With a sum of squared error (SSR) of 1.36 × 10-3, the Haldane equation is well adapted to empirical data. The improved Gombertz model also accurately predicts phenol biodegradation trends. The rate of phenol biodegradation and the lag time both increased as the initial phenol concentrations were increased. C. flaccumfaciens growth and phenol biodegradation were best achieved at a pH of 7.0 at a temperature of 28 °C incubation. A phenol biodegradation mechanism by C. flaccumfaciens has been proposed. In conclusion, this study revealed the ability of C. flaccumfaciens to promote plant growth and biodegrade phenol simultaneously. This could aid in rhizoremediation and crop yield preservation in phenol-stressed conditions.

Biovalorization of raw agro-industrial waste through a bioprocess development platform for boosting alkaline phosphatase production by Lysinibacillus sp. strain APSO

This study highlighted the exploitation of mathematical models for optimizing the growth conditions that give the highest phosphatase productivity from a newfound Lysinibacillus sp. strain APSO isolated from a slime sample. Mathematical models facilitate data interpretation and provide a strategy to solve fermentation problems. Alkaline phosphatase (ALP) throughput was enhanced by 16.5-fold compared to basal medium based on a sequential optimization strategy that depended on two-level Plackett–Burman design and central composite design. The additional improvement for volumetric productivity and specific production yield was followed in a 7 L bench-top bioreactor to evaluate microbial growth kinetics under controlled and uncontrolled pH conditions. The pH-controlled batch cultivation condition neither supported cell growth nor enhanced ALP productivity. In contrast, the uncontrolled pH batch cultivation condition provided the highest ALP output (7119.4 U L⁻¹) and specific growth rate (µ = 0.188 h⁻¹) at 15 h from incubation time, which was augmented > 20.75-fold compared to the basal medium. To the authors’ knowledge, this study is the second report that deals with how to reduce the production cost of the ALP production process via utilization of agro-industrial waste, such as molasses and food waste (eggshell), as a nutrimental source for the improvement of the newfound Lysinibacillus sp. strain APSO ALP throughput.

Removal of Phenols in Table Olive Processing Wastewater by Using a Mixed Inoculum of Candida boidinii and Bacillus pumilus: Effects of Inoculation Dynamics, Temperature, pH, and Effluent Age on the Abatement Efficiency

The main goal of this paper was to assess the ability of a combination of Candida boidinii and Bacillus pumilus to remove phenol in table olive processing water, as a function of some variables, like temperature, pH, a dilution of waste and the order of inoculation of the two microorganisms. At this purpose C. boidinii and B. pumilus were sequentially inoculated in two types of table olive processing water (fresh wastewater, FTOPW and wastewater stored for 3 months-aged wastewater, ATOPW). pH (6 and 9), temperature (10 and 35 °C) and dilution ratio (0, 1:1) were combined through a 2k fractional design. Data were modeled using two different approaches: Multifactorial Analysis of Variance (MANOVA) and multiple regression. A higher removal yield was achieved by inoculating B. pumilus prior to the yeast (192 vs. 127 mg/L); moreover, an increased efficiency was gained at 35 °C (mean removal of 200 mg/L). The use of two statistic approach suggested a different weight of variables; temperature was a global variable, that is a factor able to affect the yield of the process in all conditions. On the other hand, an alkaline pH could increase the removal of phenol at 10 °C (25-43%).

Uncovering Competitive and Restorative Effects of Macro- and Micronutrients on Sodium Benzoate Biodegradation

A model aromatic compound, sodium benzoate, is generally used for simulating aromatic pollutants present in textile effluents. Bioremediation of sodium benzoate was studied using the most abundant bacteria, Pseudomonas citronellolis, isolated from the effluent treatment plants of South Gujarat, India. Multiple nutrients constituting the effluent in actual conditions are proposed to have interactive effects on biodegradation which needs to be analyzed strategically for successful field application of developed bioremediation process. Two explicitly different sets of fractional factorial designs were used to investigate the interactive influence of alternative carbon, nitrogen sources, and inorganic micronutrients on sodium benzoate degradation. The process was negatively influenced by the co-existence of other carbon sources and higher concentration of KH₂PO₄ whereas NH₄Cl and MgSO₄ exhibited positive effects. Optimized concentrations of NH₄Cl, MgSO₄, and KH₂PO₄ were found to be 0.35, 1.056, and 0.3 mg L^–1 respectively by central composite designing. The negative effect of high amount of KH₂PO₄ could be ameliorated by increasing the amount of NH₄Cl in the biodegradation milieu indicating the possibility of restoration of the degradation capability for sodium benzoate degradation in the presence of higher phosphate concentration.

Evaluation of bioremediation and detoxification potentiality for papermaking black liquor by a new isolated thermophilic and alkali-tolerant Serratia sp. AXJ-M

There is a great need for efficiently treating papermaking black liquor because it can seriously pollute both soil and water ecosystems. In this study, the Plackett-Burman (PB) experimental design combined with response surface methodology (RSM) was used for improving the biodegradation efficiency of lignin by a new isolated thermophilic and alkali-tolerant strain Serratia sp. AXJ-M, and the results showed that a biodegradation efficiency of 70.5% was achieved under optimal culture conditions. The bacterium with ligninolytic activities significantly decreased target the parameters (color 80%, lignin 60%, phenol 95%, BOD 80% and COD 80%). The control and treated samples were analyzed by gas chromatography-mass spectrometer (GC-MS), which showed that the concentrations of a majority of low-molecular-weight compounds were decreased after biological treatment. Furthermore, toxicological, genotoxicity and phytotoxicity studies have supported the detoxification by the bacterium of black liquor. Finally, the genome sequence of the thermophilic, alkali-tolerant and lignin-degrading bacterium AXJ-M was completed, and the genetic basis of the thermophilic and alkali-resistant properties of AXJ-M was preliminarily revealed. The dyp-type peroxidase was first reported to have the potential to catalyze lignin degradation structurally. These findings suggest that Serratia sp. AXJ-M may be potentially useful for bioremediation applications for papermaking black liquor.

Efficient production of heat-stable antifungal factor through integrating statistical optimization with a two-stage temperature control strategy in Lysobacter enzymogenes OH11

Background

Heat-stable antifungal factor (HSAF) is a newly identified broad-spectrum antifungal antibiotic from the biocontrol agent Lysobacter enzymogenes and is regarded as a potential biological pesticide, due to its novel mode of action. However, the production level of HSAF is quite low, and little research has reported on the fermentation process involved, representing huge obstacles for large-scale industrial production.

Results

Medium capacity, culture temperature, and fermentation time were identified as the most significant factors affecting the production of HSAF and employed for further optimization through statistical methods. Based on the analysis of kinetic parameters at different temperatures, a novel two-stage temperature control strategy was developed to improve HSAF production, in which the temperature was increased to 32 °C during the first 12 h and then switched to 26 °C until the end of fermentation. Using this strategy, the maximum HSAF production reached 440.26 ± 16.14 mg L^− 1, increased by 9.93% than that of the best results from single-temperature fermentation. Moreover, the fermentation time was shortened from 58 h to 54 h, resulting in the enhancement of HSAF productivity (17.95%) and yield (9.93%).

Conclusions

This study provides a simple and efficient method for producing HSAF that could be feasibly applied to the industrial-scale production of HSAF.

Electronic supplementary material

The online version of this article (10.1186/s12896-018-0478-2) contains supplementary material, which is available to authorized users.

Optimization of phenol degradation by the microalga Chlorella pyrenoidosa using Plackett-Burman Design and Response Surface Methodology

Statistical optimization designs were used to optimize the phenol degradation using Chlorella pyrenoidosa. The important factor influencing phenol degradation was identified by two-level Plackett-Burman Design (PBD) with five factors. PBD determined the following three factors as significant for phenol degradation viz. algal concentration, phenol concentration and reaction time. CCD and RSM were applied to optimize the significant factors identified from PBD. The results obtained from CCD indicated that the interaction between the concentration of algae and phenol, phenol concentration and reaction time and algal concentration and reaction time affect the phenol degradation (response) significantly. The predicted results showed that maximum phenol degradation of 97% could be achieved with algal concentration of 4g/L, phenol concentration of 0.8g/L and reaction time of 4days. The predicted values were in agreement with experimental values with coefficient of determination (R(2)) of 0.9973. The model was validated by subsequent experimentations at the optimized conditions.