Initial Inoculum Concentration Research Articles

'Candidatus Liberibacter' Pathosystems at the Forefront of Agricultural and Biological Research Challenges.

'Candidatus Liberibacter' Pathosystems at the Forefront of Agricultural and Biological Research Challenges.

Production of bacterial cellulose films by Gluconoacetobacter xylinus for lipase immobilization

Bacterial cellulose (BC), a microbial polysaccharide, has chemically equivalent structure to plant cellulose with unbranched pellicle structure of only glucose monomers. Due to the unique nanostructure, BC has great potential in enzyme immobilization. In this study, the effects of different cultivation conditions including rotational speed, initial inoculum concentration and medium pH on the film-like cellulosic biomass formation of Gluconacetobacter xylinus JCM 9730 were examined. The resultant BC films were then studied for its feasibility in the immobilization of lipase, a widely used enzyme in biotechnological and industrial processes including food, pharmaceutical, chemical and paper industries. Results showed that increasing in rotational speed from 0 rpm to 200 rpm converted cellulose-producing cells to non-cellulose-producing ones, leading to a significant decline in BC film formation. The increase in initial inoculum size from 0.01 g/L to 0.1 g/L reduced sugar concentration and surface area of the medium, and therefore inhibiting the formation of film-like cellulosic biomass. In addition, the optimum pH range of Acetobacter species from 5.4 – 6.3 was found not optimal for BC film formation. The highest amount of film-like cellulosic biomass of 19.01 g/L was obtained under static condition (0 rpm) with initial cell concentration of 0.04 g/L and initial pH of 4.0. The BC film samples were then acetylated with acetic anhydride/iodine system to convert the hydroxyl groups to less hydrophilic acetyl groups and were used for lipase immobilization. Results showed that lipase immobilized on acetylated BC still maintained its lipid hydrolytic activity. It can be hence concluded that BC films produced by G. xylinus JCM 9730 were potential for lipase immobilization.

Integrated hydrothermal assisted green synthesis of ZnO nano discs and their water purification efficiency together with antimicrobial activity

The water microbial contamination is very common and different techniques are in practice for the decontamination purpose. The advance oxidation processes are being employed to mortify pathogens polluting drinking water. Heterogeneous photocatalysis under sunlight irradiation is a cost effective and remarkably proficient method for water purification. Zinc Oxide (ZnO) is a biocompatible material that has promising photo–oxidant activity. In this study, ZnO has been synthesized using Aloe vera (Av) extract assisted with hydrothermal approach. The nano disc structure of ZnO was characterized by XRD SEM, TEM, AFM, EDX, and FTIR techniques. The optical properties of ZnO@Av NDs (nano discs) evaluated by DRS and PL revealed their sunlight harvesting capability, as the calculated band gap value was 2.8 eV. The surface area and surface charge were measured by BET (5.34 m2g-1) and Zeta potential (+7.46 mV). The antibacterial activity of ZnO@Av NDs was studied against Salmonella typhimurium as a function of various process variables i.e., photocatalyst loading, sunlight exposure time, and bacterial inoculum size. The bactericidal reaction parameters were optimized statistically by Response Surface Methodology (RSM) on exposure to direct sunlight (average solar flux was 650 KWh/m2) at pH 7. As optimized conditions, 100 μL initial inoculum concentration of S. typhimurium was treated with 60 μg/mL of ZnO@Av NDs suspension under sunlight irradiation of 5 h, antibacterial index obtained was 6.8. The MIC and MBC for ZnO@Av NDs against S. typhimurium were 50 μL and 100 μL, respectively. It has been observed that ZnO@Av NDs lower the optical density of water that contains S. typhimurium. The photocatalytic purification of water using ZnO@Av NDs is safe and cost-effective method under sunlight irradiation, which could possibly be employed for the wastewater purification.

Volatile organic compounds produced by Pseudomonas fluorescens ZX as potential biological fumigants against gray mold on postharvest grapes

Volatile organic compounds (VOCs) produced by antagonistic microorganisms have the potential for controlling postharvest diseases on fruit and vegetables. In this study, the biocontrol efficacy of VOCs emitted by Pseudomonas fluorescens ZX was determined in vitro and in vivo against gray mold, caused by Botrytis cinerea, on grapes. In vitro, application of VOCs produced by bacterial suspension of P. fluorescens ZX at initial inoculum concentration of 1 × 109 colony-forming units (CFU)/mL inhibited B. cinerea mycelial growth from 52 to 23 mm and spore germination from 88.56 to 39.67%. In vivo tests indicated that, for grapes, disease incidence and disease index were markedly reduced by VOCs from P. fluorescens ZX incubated on NA plates, in NB, and on healthy grapes. Pre-fumigation with VOCs could inhibit development of gray mold on grapes. Furthermore, P. fluorescens ZX-producing VOCs exhibited favorable effects on postharvest natural decay of grapes. In vitro testing of selected pure chemicals demonstrated that dimethyl trisulfide (20 μL/L), dimethyl disulfide (40 μL/L), geranyl formate (640 μL/L), acetic acid (160 μL/L), butyric acid (320 μL/L), 2-methylbutyric acid (160 μL/L), isobutyric acid (160 μL/L) and isovaleric acid (320 μL/L) could completely inhibit mycelial growth of B. cinerea on PDA plates. These eight substances also exerted a strong inhibitory effect on gray mold on grapes. Additionally, SEM analysis showed that VOCs could affect the morphological and structural characteristics of B. cinerea both in vitro and in vivo. Collectively, VOCs produced by P. fluorescens ZX are promising for biocontrol of gray mold on grapes through fumigant action.

Kinetics of Staphylococcus aureus growth and Enterotoxin A production in milk under shaking and static conditions

Numerous studies on bacterial growth or survival predictive models have been conducted since the establishment of predictive microbiology. However, limited research focused on the prediction of bacteria-producing enterotoxins, which are often the causative agents of food-borne diseases. This study aimed to determine an appropriate kinetic model of staphylococcal enterotoxin A (SEA) production in milk after contamination with Staphylococcus aureus. An S. aureus strain producing SEA was inoculated into milk with an initial inoculum concentration of approximately 3.0 log CFU/mL. All samples were incubated for 30–48 h at 20 °C ± 1 °C, 28 °C ± 1 °C, and 36 °C ± 1 °C separately under shaking or static conditions. Duplicate samples were carried out at appropriate intervals to count the number of S. aureus colonies and detect the concentration of SEA. Experimental results showed that the SEA concentration curves under all experimental conditions were sigmoidal and consisted of three phases: lag, exponential, and stationary. Thus, the modified Gompertz model was used to describe the profile of SEA concentration in milk during the incubation. A good fitting accuracy (R2 > 0.97) indicated that the modified Gompertz model was appropriate. In addition to temperature, shaking during incubation also affected the maximal production rate of SEA and the maximal SEA concentrations, and shortened the lag phase at lower incubation temperatures, suggesting that the mechanical movements (e.g., stirring, pumping, and flowing) during the milk processing would increase the risk of SEA occurrence. Besides, the time to detection (TTD) of SEA was found to range from 3 to 24.5 h at temperatures of 36 °C ± 1 °C–20 °C ± 1 °C, at which time the concentrations of S. aureus ranging from 5.0 log CFU/mL–6.9 log CFU/mL at the TTD. This study contributed to understanding the kinetics of SEA production and the possible factors affecting the synthesis of SEA during the manufacturing of liquid foods, such as milk.

Screening of microfungi for lipolytic activity and optimization of process parameters in lipase production by solid substrate fermentation using selected microfungi (Penicillium aurantiogriseum)

In the present study, eighty-four strains of microfungi were screened for lipolytic activity, and Penicillium aurantiogriseum showing the highest enzyme activity was selected. Then extracellular lipase production from this species was carried out using the solid state fermentation (SSF) method, in which various agricultural wastes were used as substrates. Among the various agricultural wastes used in SSF, sunflower pulp was determined as the best solid substrate. Optimum fermentation conditions were found as follows: 6-day incubation time at 25 oC and moisturizing liquid pH: 5.5 (distilled water), initial moisture level 75% (w/v), initial inoculum concentration 1 ml (1x106 spores/ml), and 1% sesame oil as a carbon source. As a result of the optimum conditions, the volume activity was recorded as 0.4 U/ml, and the specific enzyme activity was obtained as 1.13 U/mg.

Synthesis and antibacterial activities of quaternary ammonium salts with different alkyl chain lengths grafted on polyvinyl alcohol-formaldehyde sponges

Antibacterial polyvinyl alcohol-formaldehyde (PVF) sponges containing quaternary ammonium salts (QA) with different alkyl chain lengths are obtained through the grafting reaction of QA onto the PVF network under alkaline conditions. The grafting percentages of obtained PVF-g-QA sponges are in the range of 1.1–1.6%. As-prepared PVF-g-QA sponges show average pore sizes ranging from 60 μm to 90 μm with high porosity and interconnected pore structure. PVF-g-QA sponges with different alkyl chain lengths display the absorption capacity (Qs) of 13.3–14.2 g·g−1 in deionized water, 13.9–14.8 g·g−1 in saline solution, and 13.9–14.8 g·g−1 in artificial blood and can attain absorption equilibrium within 1 min. Notably, the PVF-g-QA sponges demonstrate excellent antibacterial effects on both S. aureus and E. coli bacteria strains. With high initial inoculum concentration (1 × 108 CFU/mL), with increasing the alkyl chain length of QA, the antibacterial activities of PVF-g-QA sponges against E. coli increase from 20.47% to 99.98% firstly and then decrease to 92.91%, the antibacterial activities against S. aureus increase from 16.67% to 99.96% and then decrease to 93.21%. None of the samples have cytotoxicity for cells. The as-prepared PVF-g-QA sponges with remarkable absorption capacity and excellent antibacterial performance can be considered as a new kind of antibacterial functional material.

Performance evaluation of hydroponic system for co-cultivation of microalgae and tomato plant

Conventional hydroponic units producing disease free plants with 30–40% faster growth rate are regarded as a promising agricultural alternative in case of unfertile/metal contaminated soil. However, most nutrients in hydroponics medium remain unused and are drained off creating environmental pollution. To reduce the nutrient load and eutrophication effects, cocultivation of plant and microalgae in the hydroponic units has attracted the attention of researchers over the past few years. The present study aims to explore the influence of initial inoculum concentration of a native algal consortium over the performance of hydroponic system. Cocultivation of tomato plant with varying initial inoculum algal concentration of 0.2–0.8 mg/ml, showed that 0.8 mg/ml concentration resulted in positive interactions between microalgae and plant, with algal and plant productivity of 0.149 ± 0.024 and 0.328 ± 0.087 g/m2/d respectively after 42 days. Higher chlorophyll accumulation, along with nutritionally rich algal and plant biomass revealed lack of unwanted competition during cocultivation. Increase in dissolved oxygen during cocultivation was corroborated with efficient root respiration. Highly developed roots also provided adequate metabolic energy thus significantly increasing the nutrient uptake and accumulation, thereby reducing the nutrient load during drainage. The supernatant after algal harvesting (recycled media) supported plant growth for 24 days due to limited nutrients. Such system with microalgae symbiotically favouring plant productivity and simultaneous nutrient load reduction would ultimately support in attaining sustainable agriculture.

Survival of Salmonella enterica subsp. enterica serovar Javiana and Listeria monocytogenes is dependent on type of soil-free microgreen cultivation matrix.

This study measured the survival of Listeria monocytogenes and Salmonella enterica subsp. enterica serovar Javiana over a 10-day period on four soil-free cultivation matrix (SFCM) types in the absence of microgreens and fertilizers. Coco coir (CC), a Sphagnum peat/vermiculite mix, Biostrate® and hemp mat samples were inoculated with 3×106 CFU per ml bacteria, incubated at room temperature, and analysed on day 0, 1, 3, 6, and 10. Statistically significant differences in pathogen survival were observed across multiple time points for hemp and Biostrate compared to CC, peat and bacteria in phosphate buffered saline (PBS) (P<0·05). S. Javiana showed greater overall survival compared to Listeria (P<0·0002). By day 10, S. Javiana persisted at the initial inoculum concentration for hemp and Biostrate while declining by 1-2 log CFU per ml in CC, peat and PBS. Listeria also persisted at the initial concentration in hemp and Biostrate but decreased to 1 log CFU per ml in peat and below the detection limit in CC and PBS. Overall, there are survival differences between bacterial pathogens in SFCM used in microgreen production systems. To our knowledge, this is the first comparison of survival among SFCM involving a S. enterica serovar and L. monocytogenes, and the first study comparing CC, Biostrate and hemp. Microgreens production systems predominantly utilize soil alternatives, and it is not well-understood how pathogen transmission risk may be affected by the type of SFCM. The results of this study impact the microgreen industry as media selection may be used to reduce the risk of bacterial pathogen proliferation and transmission to the plant potentially resulting in potential foodborne illness.

Kinetic modelling of ethanolic fermented tomato must (Lycopersicon esculentum Mill) in batch system: influence of sugar content in the chaptalization step and inoculum concentration

This work studies the production of alcoholic beverages using tomato pulp, aiming at characterizing fermentation kinetics by modelling. Batch fermentation tests were carried out in order to assess inoculum concentration, ranging between 1, 3 and 5 g/L, with sugar concentrations at 55, 110, 230 g/L and tomato must containing 20 g/L of pulp concentration at 30 °C and pH 5.5. The best process operating conditions were identified as 230 g/L of sugar and 5 g/L of inoculum, having obtained a tomato wine with 101.5 g/L of ethanol and 99.5% of biochemical efficiency. The kinetic constants obtained (µmax) ranged between 0.2–0.5 day−1 and a half-saturation constant (Ks) with an average value of 17.90 ± 1.08 g/L, exhibiting slow fermentation, with the exponential process lasting for approximately 4 days. The substrate consumption rates and ethanol yield reached maximum values of 4.54 g/(L⋅h) and 1.39 g/(L⋅h), respectively. The conversion factors of YX/S and YP/S were obtained as a function of initial substrate concentration (sucrose) and inoculum concentration. No sharp inhibition rates were observed, with only the Monod Model being used to describe the process.

The Optimal Condition on the Growth of Green Haematococcus Pluvialis as one of the Future Natural Resources

In the developing world nowadays, the need of antioxidants as counteracting free radicals becomes more and more. Astaxanthin is a carotenoid pigment with high antioxidant content. It can be obtained from natural sources or chemical synthesis. Haematococcus pluvialis is one of natural sources of astaxanthin which accumulates large amounts of astaxanthin under stressful condition. The growth of H. pluvialis in the green phase determines the amount of astaxanthin that can produced. It is influenced by various conditions such as amount and type of growing medium, light intensity, pH of medium, temperature, and initial inoculum concentration. The goal of this research is to obtain the optimum condition on the growth of H. pluvialis at the green stage using the experimental design i.e. Central Composite Design (CCD). The variables observed were the effect of the initial inoculum concentration (25-35% -v/v), the concentration of nutrients (1-2 mL/L liquid water), and the types of growth medium (Walne’s and BG-11). Before the experiment, H. pluvialis was cultured until its optical density (OD = 1 – 1.2). The responses observed were the cell density based on optical density (OD) using a spectrophotometer and cell number counted by using haemacytometer every day during 5 days. The results were examined using the Design Expert 7.0. It showed that the optimal growth conditions of H. pluvialis cells was in BG-11 medium with initial inoculum concentration and the number of nutrients were 37, 07% and 1.5 mL/L respectively. The highest cell number was found 23, 75 x 106 cells / mL in the 3rd day. Whereas by using Walne media, the optimum condition was obtained at the initial inoculum concentration and the amount of nutrients were 35% and 2 mL respectively. And the highest cell density number obtained was 17, 5 x 106 cells / mL on the 3rd day.

Kinetic modeling of microalgae growth and CO2 bio-fixation using central composite design statistical approach

The optimum growth (μ), CO2 bio-fixation (RCO2) rates and the energy ratio (ER) of microalgae Chlorella vulgaris (C.v) were identified using central composite design statistical approach (CCD-SA). μ and RCO2 parameters including temperature of photobioreactor (TPBR), concentration of CO2 (CCO2 ), nutrients (carbon, nitrogen and phosphorus), gas flow rate (Qgas), initial inoculum concentration (INden) and the solar light intensity (Itot) were considered. Results revealed mild operational conditions in the range 20–25 °C, CCO2 of 2.5–20% (v/v), Qgas of 0.5–0.8 vvm and Itot of 50–200 μE/m2·s would generate considerable μ and RCO2. The highest μ and RCO2 with a significant ER of 19.5 were generated under CCD-SA optimized parameters of T = 25 °C, CCO2 = 20%, Qgas = 0.5 ± 0.05 (Std. Dev. = 0.04) vvm, total inorganic nitrogen (TN) = 19 ± 2 (Std. Dev. = 0.1) mg-N/L, Total phosphorous = 7 ± 1 (Std. Dev. = 0.7) mg-P/L, COD = 20 ± 2 (Std. Dev. = 0.5) mg-COD/L, INden = 0.52 ± 0.01 (Std. Dev. = 0.05) mg/L and Itot = 150 ± 2(Std. Dev. = 0.6) μE/m2s). Microalgae technology can be considered as a promising technology for CO2 bio-fixation in a large scale with a sustainable value of the produced biomass for biofuel production.

Optimization of cultivation conditions for Microcystis aeruginosa for biodiesel production using response surface methodology

BackgroundBiodiesel is expected to play a key role in the development of a sustainable, economical, and environmentally safe source of energy. The third generation of biodiesel is derived from microalgae and cyanobacteria that have sufficient amount of oil. The optimization of biomass and oil content in biodiesel production based on algal cultivation relies upon several factors. The present experimental work aims at optimizing some of the cultivation conditions to obtain maximum oil and biomass yield and create a prediction model that describe the effect of the initial inoculum concentration, and irradiance on the biomass yield and oil concentration were designed using Design Expert 6.0.8.ResultsThe results revealed that the optimum surface-to-volume ratio for the airlift bubble column photobioreactor was 0.9, and the most applicable model for describing Microcystis aeruginosa growth was the hyperbolic tangent model with a model constant value of 1.294 mg·L− 1·d− 1/μmol·m− 2·s− 1. The optimum cultivation conditions were 81 μmol·m− 2·s− 1 irradiance and 67 mg·L− 1 initial inoculum concentration, and these conditions achieved a biomass yield of 163 mg·L− 1·d− 1 and an oil concentration of 143 mg·L− 1.ConclusionsThis work focused on the cultivation of microalgae in closed systems. Cyanobacteria as M. aeruginosa has high lipid content, and high lipid productivity makes it suitable as a lipid feed stock for biodiesel production. The response surface method was the most suitable route to study the simultaneous influence of irradiance and initial inoculum concentration through statistical methods as well as to establish a model for predicting the biomass yield and oil concentration of M. aeruginosa.

Nutrient and heavy metal removal from piggery wastewater and CH4 enrichment in biogas based on microalgae cultivation technology under different initial inoculum concentration.

Three microalgae-based treatment technologies were applied for removing nutrients in piggery wastewater and CO2 in biogas simultaneously. Chlorella vulgaris (C.vulgaris), Scenedesmus obliquus (S.obliquus), and Neochlorisoleoabundans (N.oleoabundans) were selected for mono-cultivation or co-cultivation with fungi or activated sludge. The effects of initial inoculum concentration (low of 62.06±6.23mg/L, medium of 121±9.34mg/L, and high of 180±12.78mg/L) of microalgae/algal symbiont on the pollutant removal efficiency were evaluated. The results showed that cultivation of S.obliquus with activated sludge had a relatively high CO2 and nutrients removal efficiency at a medium concentration of initial inoculum. The highest removal efficiency of total organic carbon, total nitrogen, and total phosphorus in piggery wastewater was 87.29%, 87.26%, and 90.17% by co-cultivation of S.obliquus with activated sludge. The highest CO2 removal of 64.28% could be achieved under co-cultivation of S.obliquus and fungi at medium initial inoculum concentrations. This work will be helpful to promote the study of microalgae-based biogas upgrading and piggery wastewater purification. PRACTITIONER POINTS: Nutrient and CO2 were efficiently removed in moderate microalgal initial inoculum. Scenedesmus obliquus-activated sludge cultivation achieved the highest nutrient removal. Co-cultivation of S.obliquus and fungi showed the highest CO2 removal. Zinc was removed efficiently in high microalgal initial inoculum. Chlorella vulgaris/S.obliquus-activated sludge performed economically.

An experimental and computational study of biosurfactant production from soy molasses

Mathematical modeling was performed of rhamnose production in a batch process, with model validation and optimization of a continuous fixed bed process. The batch experiments were performed for 72 h in a rotary incubator at 27 ± 1.0 °C and 120 rpm, with an initial inoculum concentration of 3 g/L in 150 mL of soy molasses at 100 g/L. Parameter determination was performed using multiple response nonlinear regression, with integration of a set of differential equations, employing the Runge–Kutta algorithm and application of the Contois model. The model was fitted to the experimental data and the sum of squared residuals was 47.61. The fitted parameters were validated in an experiment employing a column operated continuously at a flow velocity of 0.288 cm/h (flow rate of 0.02 mL/min), applying the plug flow reactor (PFR) and axial dispersion models. The optimal conditions were determined by the graphical assessment of the response variable behavior. The best validation results were obtained for the axial dispersion model. The optimum velocity was 0.3 cm/h, with less significant improvements in productivity at higher flow rates, for the substrate concentration range studied.

Co-pelletization of microalgae and fungi for efficient nutrient purification and biogas upgrading

The fungi-assisted microalgae pellets were cultivated to simultaneously purify biogas slurry and biogas. Results demonstrated that the optimized culture conditions for the pellets were at the shaking speed of 160 rpm, initial inoculum concentration of 1.0 × 106 spores L−1 for microalgal cells, fungi/algae ratio of 1:10, mixed medium/simulated biogas slurry ratio of 3:7 incubated at a light intensity of 200 μmol m−2 s−1. Moreover, biogas slurry purification and biogas upgrading were successfully achieved by co-cultivation of fungi-assisted microalgae pellets at mixed light wavelength of red:blue of 5:5. The highest removal efficiency of COD, TN, TP and CO2 were 92.17 ± 5.28%, 89.83 ± 4.36%, 90.31 ± 4.69% and 74.26 ± 3.14%, respectively. These results will provide a theoretical foundation for large-scale biogas slurry purification and biogas upgrading using fungi-assisted microalgal pellets.

Xylitol production on sugarcane biomass hydrolysate by newly identified Candida tropicalis JA2 strain.

Xylitol is a building block for a variety of chemical commodities, besides being widely used as a sugar substitute in the food and pharmaceutical industries. The aim of this work was to develop a microbial process for xylitol production using sugarcane bagasse hydrolysate as substrate. In this context, 218 non-Saccharomyces yeast strains were screened by growth on steam-exploded sugarcane bagasse hydrolysate containing a high concentration of acetic acid (8.0g/L). Seven new Candida tropicalis strains were selected and identified, and their ability to produce xylitol on hydrolysate at low pH (4.6) under aerobic conditions was evaluated. The most efficient strain, designated C.tropicalis JA2, was capable of producing xylitol with a yield of 0.47g/g of consumed xylose. To improve xylitol production by C.tropicalis JA2, a series of experimental procedures were employed to optimize pH and temperature conditions, as well as nutrient source, and initial xylose and inoculum concentrations. C.tropicalis JA2 was able to produce 109.5g/L of xylitol with a yield of 0.86g/g of consumed xylose, and with a productivity of 2.81g·L·h, on sugarcane bagasse hydrolysate containing 8.0g/L acetic acid and177 g/L xylose, supplemented with 2.0g/L yeast nitrogen base and 4.0g/L urea. Thus, it was possible to identify a new C.tropicalis strain and to optimize the xylitol production process using sugarcane bagasse hydrolysate as a substrate. The xylitol yield on biomass hydrolysate containing a high concentration of acetic acidobtained in here is among the best reported in the literature.

Optimization of microalgae Scenedesmus SP. growth rate using a central composite design statistical approach

In this research, growth rate of microalgae Scenedesmus sp. was modified by optimizing four effective factors. The operational energy efficiency factor (OEEf) of the photobioreactor was also considered in parallel. A central composite design statistical approach was implemented to evaluate the results. These factors were carbon dioxide concentration (0.038 (air), 2.0, 5.0, 7.0, 10.0%), aeration rate (0.2, 0.5, 1.5, 3.0, 4.0 vvm), initial inoculum concentration (0.140–0.430 g/l) and gas diffuser diameter (0.4, 1.0, 2.6, 4.0, 5.0 mm). All the factors were very significant at the defined ranges. The diffuser diameter also showed different effect when either low or high carbon dioxide concentration was applied. The optimized values (6.02% CO2, 0.39 vvm flow rate, 3.7 mm diffuser diameter and 0.180 g/l initial inoculation) would result the maximum growth rate of 0.525 g/l.d and high OEEf of 19.5 which was very significant. It was concluded that microalgae technology is a promising solution for carbon dioxide sink in large scale and biofuel production after optimizing the biomass production rate.

Effects of the treatment parameters on the efficacy of the inactivation of Salmonella contaminating boiled chicken breast by in-package atmospheric cold plasma treatment

The effects of surface coating, microbial loading, surface-to-volume ratio, sample stacking, mixing of samples with romaine lettuce, and shaking of the samples on the inactivation of Salmonella contaminating boiled chicken breast (BCB) cubes using in-package atmospheric dielectric barrier discharge cold plasma (ADCP) treatment at 38.7 kV were investigated. Whey protein coating increased the ADCP treatment efficacy in inactivating Salmonella on BCB cubes; the D-value increased from 0.2 to 1.3 min when the initial inoculum concentration increased from 3.8 to 5.7 log CFU/sample. ADCP decontaminated stacked BCB samples uniformly, and shaking during the treatment increased the inactivation rate. The concentrations of chicken protein isolate, water, and soybean oil in a chicken breast model food that resulted in the highest Salmonella reduction (1.7 log CFU/sample) were 20.5%, 68.9%, and 10.6%, respectively. ADCP treatment did not affect the color and tenderness of the model food, irrespective of its composition. The present study indicated that ADCP is a feasible technology to decontaminate prepackaged ready-to-eat meat cube products.

Using response surface methodology to improve the L-asparaginase production by Aspergillus niger under solid-state fermentation

Abstract Microbial L-asparaginase have been used as a therapeutic agent in the treatment of acute lymphoblastic leukemia and Hodgkin's disease. In addition to clinical use, L-asparaginases have been used in foods to reduce the formation of acrylamide. L- asparaginase production is carried out mainly by submerged fermentation (SmF). However, solid-state fermentation (SSF) offers potential benefits compared with submerged fermentation, such as the use of low-cost agro-industrial residues as the substrate, which is very attractive for bioprocessing. The main objective of this study was to evaluate the use of agro-industrial wastes, including wheat bran, soybean meal, rice meal, chicken feather meal, chicken viscera meal and passion fruit peel flour, for L-asparaginase production by Aspergillus niger LBA 02 under solid-state fermentation. Among the substrates, the highest L-asparaginase activity was obtained using passion fruit peel flour (2380.11 U/gds) after 48 h of fermentation at 30 °C. The effects of temperature, initial moisture content (%) and inoculum concentration (spores/g) on the L-asparaginase production were evaluated using passion fruit peel meal as a substrate using Central Composite Rotatable Design (CCRD) with 17 runs. An increase in L-asparaginase activity (3746.78 U/gds) was obtained using the optimized conditions of passion fruit peel flour with an initial moisture content of 60% and inoculum concentration of 2.1 106 spores/g after 24 h of fermentation at 25 °C. It was observed that the process optimization resulted in a 57% increase in enzyme production compared with the initial values obtained in the “one-factor-at-a-time” method.