Loofa (Luffa cylindrica) sponge as a carrier for microbial cell immobilization

Enhanced removal organic compounds and particles from cooking fume using activated sludge scrubber filled loofah: From performance to the mechanism

The catering industry's growth has resulted in cooking fume pollution becoming a major concern in people's lives. As a result, its removal has become a core research focus. Natural loofah is an ideal biofilm carrier, providing a conducive environment for microorganisms to grow. This study utilized natural loofah to fill domesticated activated sludge in a bioscrubber, forming biofilms that enhance the ability to purify cooking fume. This study found that the biomass of loofah biofilms per gram is 104.56 mg. The research also determined the removal efficiencies for oils, Non-methane total hydrocarbons (NMHC), PM2.5, and PM10 from cooking fumes, which were 91.53%, 67.53%, 75.25%, and 82.23%, respectively. The maximum elimination capacity for cooking fumes was found to be 20.7 g/(m3·h). Additionally, the study determined the kinetic parameters for the biodegradation of oils (Kc and Vmax) to be 4.69 mg L-1 and 0.026 h-1, respectively, while the enzyme activities of lipase and catalase stabilized at 75.50 U/mgprots and 67.95 U/mgprots. The microbial consortium identified in the biofilms belonged to the phylum Proteobacteria and consisted mainly of Sphingomonas, Mycobacterium, and Lactobacillus, among others.

Non-invasive morphological characterization of cellular loofa sponges using digital microscopy and micro-CT

Loofa sponge is a naturally-grown and decomposable material providing high specific surface area and high porosity for potential application as an environmentally-friendly catalyst carrier. In this work, cellular samples of various loofa types cut from different fiber network regions of the fruits were studied in detail using non-invasive imaging techniques. Digital microscopy was applied to characterize the cellular fiber network, which revealed a honeycomb structure in the core region and a sandwich structure in the wall region. Furthermore, reconstructed three-dimensional (3D) morphological images of the loofa samples obtained via micro-tomography (micro-CT) were utilized to extract the geometrical properties cell size, window diameter and strut thickness as well as porosity and volume-specific surface area. The reconstructed loofa samples revealed porosities of about 92% and specific surface areas up to 2057 m2/m3. In addition, the geometrical properties of manufactured solid foams (ceramic and polyurethane) were also determined via micro-CT and compared with loofa sponge. Finally, the different characteristic cell dimensions were employed to predict the porosity and specific surface area with available geometrical correlations. Deviations between correlation and measurement data (±16%) can be attributed to the peculiarity of the loofa cellular fiber network, which is somewhat different from the tetradecahedral-shaped geometry commonly used as the basis for most of the available correlations.

Production of bacterial cellulose using Gluconacetobacter kombuchae immobilized on Luffa aegyptiaca support

The present work report for the first time on the production of bacterial cellulose (BC) using natural loofa sponge (Luffa aegyptiaca) as a scaffold for the immobilization of Gluconacetobacter kombuchae. Bacterial cellulose (BC) are recently gained more attention in several fields including biological and biomedical applications due to their outstanding physico-chemical characteristics including high thermal stability, easy biodegradability, good water holding capacity, high tensile strength, and high degree of polymerization. The increase in requirement of alternative method for the enhancement of BC production under economical aspect develops a positive impact in large scale industries. In this study, Luffa aegyptiaca (LA) was introduced in a separate fermentation medium so as to enhance the concentration of BC production by Gluconacetobacter kombuchae. Different process/medium parameters such as initial pH, static/shaking condition, inoculum size, nitrogen source, C/N ratio, supplements (ethanol and acetic acid) were analysed for the production of bacterial cellulose using LA support. The maximum yield of BC was obtained using following condition: culturing condition -shaking; initial pH - 5.5; nitrogen source- yeast extract, C/N ratio - 40 and supplement-ethanol. The characterization of the BC was examined using Fourier Transform Infra-Red spectroscopy and thermo gravimetric analysis. The biofilm formation on the surface of LA was examined by SEM photographs. Thus, implementation of LA as a support in shaking fermentation under suitable medium/process variables enhanced the BC production.

DERA in Flow: Synthesis of a Statin Side Chain Precursor in Continuous Flow Employing Deoxyribose-5-Phosphate Aldolase Immobilized in Alginate-Luffa Matrix

Statins, cholesterol-lowering drugs used for the treatment of coronary artery disease (CAD), are among the top 10 prescribed drugs worldwide. However, the synthesis of their characteristic side chain containing two chiral hydroxyl groups can be challenging. The application of deoxyribose-5-phosphate aldolase (DERA) is currently one of the most promising routes for the synthesis of this side chain. Herein, we describe the development of a continuous flow process for the biosynthesis of a side chain precursor. Design of experiments (DoE) was used to optimize the reaction conditions (pH value and temperature) in batch. A pH of 7.5 and a temperature of 32.5 °C were identified to be the optimal process settings within the reaction space considered. Additionally, an immobilization method was developed using the alginate-luffa matrix (ALM), which is a fast, simple, and inexpensive method for enzyme immobilization. Furthermore, it is non-toxic, biodegradable, and from renewable resources. The final continuous process was operated stable for 4 h and can produce up to 4.5 g of product per day.

Effects of various inhibitory substances and immobilization on ethanol production efficiency of a thermotolerant Pichia kudriavzevii

BACKGROUND

Although bioethanol production has been gaining worldwide attention as an alternative to fossil fuel, ethanol productivities and yields are still limited due to the susceptibility of fermentation microorganisms to various stress and inhibitory substances. There is therefore an unmet need to search for multi-stress-tolerant organisms to improve ethanol productivity and reduce production cost, particularly when lignocellulosic hydrolysates are used as the feedstock.

RESULTS

Here, we have characterized a previously isolated Pichia kudriavzevii LC375240 strain which is thermotolerant to high temperatures of 37 °C and 42 °C. More excitingly, growth and ethanol productivity of this strain exhibit strong tolerance to multiple stresses such as acetic acid, furfural, formic acid, H₂O₂ and high concentration of ethanol at 42 °C. In addition, simple immobilization of LC375240 on corncobs resulted to a more stable and higher efficient ethanol production for successive four cycles of repeated batch fermentation at 42 °C.

CONCLUSION

The feature of being thermotolerant and multi-stress-tolerant is unique to P. kudriavzevii LC375240 and makes it a good candidate for second-generation bioethanol fermentation as well as for investigating the molecular basis underlying the robust stress tolerance. Immobilization of P. kudriavzevii LC375240 on corncobs is another option for cheap and high ethanol productivity.

Ethanol production from sweet sorghum by Saccharomyces cerevisiae DBKKUY-53 immobilized on alginate-loofah matrices

Ethanol production from sweet sorghum juice (SSJ) using the thermotolerant Saccharomyces cerevisiae strain DBKKUY-53 immobilized in an alginate-loofah matrix (ALM) was successfully developed. As found in this study, an ALM with dimensions of 20×20×5mm3 is effective for cell immobilization due to its compact structure and long-term stability. The ALM-immobilized cell system exhibited greater ethanol production efficiency than the freely suspended cell system. By using a central composite design (CCD), the optimum conditions for ethanol production from SSJ by ALM-immobilized cells were determined. The maximum ethanol concentration and volumetric ethanol productivity obtained using ALM-immobilized cells under the optimal conditions were 97.54g/L and 1.36g/Lh, respectively. The use of the ALM-immobilized cells was successful for at least six consecutive batches (360h) without any loss of ethanol production efficiency, suggesting their potential application in industrial ethanol production.

Formaldehyde degradation by Ralstonia eutropha in an immobilized cell bioreactor

The formaldehyde (FA) degradation ability of the loofa-immobilized Ralstonia eutropha cells in a packed bed reactor was modeled using a statistically based design of the experiment (DOE) considering application of response surface methodology (RSM). The simultaneous effects of four operative test factors on the cells performance in terms of FA degradation rate and extent of the chemical oxygen demand (COD) removal were monitored. The combination of factors at initial FA concentration of 629.7 mg L(-1)h(-1), recycling substrate flow rate of 4.4 mL min(-1), aeration rate of 1.05 vvm, and the system's temperature of 28.8°C resulted the optimal conditions for the FA biodegradation rate and COD removal efficiency. Loofa porous structure was found to be a protective environment for the cells in exposing to the toxic substances and the scanning electron microscopy (SEM) images revealed extensive cells penetration within this support. Oxygen transfer analysis in the form of evaluating K la value was also carried out and at the optimum conditions of the DOE was equaled to 9.96 h(-1)and oxygen uptake rate was 35.6 mg L(-1)h(-1).

Aerobic pretreatment of olive oil mill wastewater using Ralstonia eutropha

Olive oil mill wastewater (OMW) has a high polluting power, with total phenolics (TP) around 2.5 g l(-1) and chemical oxygen demand (COD) 85 g l(-1). Biological systems offer advantages in treating this type of agro-industrial wastewater. The performance of phenol-adapted Ralstonia eutropha for aerobic biotreatment of OMW has been studied, and a TP concentration of 250 mg l(-1) found to be fully degraded within 24 h. This simple procedure may be adopted as a pretreatment prior to the normal aerobic or anaerobic techniques used for treating OMW. The biodegradative capability of this non-pathogenic gram-negative bacterium towards the TP and COD content of OMW has been evaluated. The adapted free cells were found able to decrease TP and COD in the undiluted OMW by 56% and 42%, respectively. The Monod equation was found suitable to describe the capacity of the cells for growing on undiluted OMW, giving micromax 0.083 per day and Ks = 1846 mg l(-1). Using a packed-bed reactor the performance of loofa-immobilized R. eutropha was assessed and the reduction in TP and COD shown to be 73% and 64%, respectively.

Alginate-loofa as carrier matrix for ethanol production

An alginate-loofa matrix was developed as a cell carrier for ethanol fermentation owing to its porous structure and strong fibrous nature. The matrix was effective for cell immobilization and had good mechanical strength and stability for long-term use. After a storage period of 4 months, yeast cells remained firmly immobilized and active.

Acetylation of loofa (Luffa cylindrica) sponge as immobilization carrier for bioprocesses involving cellulase

The feasibility of using loofa sponge for immobilization of cellulase-producing microorganisms was investigated by acetylating loofa sponge. Acetylation was achieved by autoclaving process of loofa sponge immersed in acetic anhydride at various temperatures for various times. The degree of acetylation, as inferred by the weight percentage gain (WPG), was enhanced by increasing both temperature and the duration of acetylation. The acetylation of a piece of loofa sponge in an autoclave at 120 degrees C for 20 min resulted in a WPG of about 8%, which was sufficient to protect the loofa sponge against cellulose degradation. The acetylated loofa sponge prepared under this condition was not decomposed by commercial cellulase and its structure was maintained for more than 720 h during repeated-batch treatments with commercial cellulase. A flocculating yeast (Saccharomyces cerevisiae IR-2) and a fungus (Trichoderma reesei QM9414) were successfully immobilized in the acetylated loofa sponge. In each case, the percentage of immobilized cells was as high as that obtained using nonacetylated loofa sponge. Acetylation had no adverse effects on cell growth and immobilization of T. reesei QM9414, as well as on cell growth and ethanol production by S. cerevisiae IR-2. T. reesei QM9414 immobilized on an acetylated loofa sponge was successfully used for repeated-batch cellulase production from commercial cellulose powder. Although the acetylated loofa sponge showed a slight weight loss, it was not disintegrated by activated sludge. The results obtained in this study showed that acetylated loofa sponge is suitable as an immobilization carrier for bioprocesses involving cellulase.

Production of lactic acid with loofa sponge immobilized Rhizopus oryzae RBU2-10

Lactic acid production by Rhizopus oryzae RBU2-10 immobilized in loofa sponge was evaluated. Shape and texture of loofa sponge, which was obtained from the mature dried fruit of Luffa cylindrica, remained intact after its treatment with buffers of varying pH and following its repeated autoclaving for up to four cycles (121 degrees C, 20 min per cycle). The medium having four pieces of loofa sponge (1.008 cm(3)) per 100 ml medium and inoculated with 3 x1 0(6) spores ml(-1) resulted maximum production (80.75 g l(-1)) of lactic acid in 48 h of fermentation. Repeated batch fermentation for lactic acid production could be carried out for 10 cycles. Remarkably higher levels of productivity (1.66-1.84 g l(-1)h(-1)) was obtained during first five cycles of fermentation with a maximum productivity (1.84 g l(-1)h(-1)) obtained during third cycle of fermentation.

Degradation of carbendazim and 2,4-dichlorophenoxyacetic acid by immobilized consortium on loofa sponge

A fungicide, carbendazim (methyl-2-benzimidazole carbamate; MBC), and a herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), could be simultaneously degraded by a microbial consortium obtained from several soil samples in Japanese paddy fields with enrichment continuous culture. The degradation ability of the consortium was increased by immobilization on loofa (Luffa cylindrica) sponge in comparison with that of free-living consortium. MBC and 2,4-D were completely degraded within 5.5 d and 1.5 d, respectively. The toxicity of these pesticides in culture medium to Daphnia magna was reduced by treatment with the consortium corresponding to their degradation. The degradation ability of the immobilized consortium at pHs in the range from 6 to 9, at temperatures from 15 degrees C to 37 degrees C, and at low NH(4)(+)-N concentrations (1-10 mg/l) was not very different from that under the basal condition (pH 7, 30 degrees C, 424 mg/l NH(4)(+)-N and 472 mg/l PO(4)(3)(-)-P). At low pHs 4 and 5, the ability was significantly lower than that of the basal condition. Moreover, incubation at low PO(4)(3)(-)-P concentrations (1-10 mg/l) caused a decrease in pH at which the degradation ability also became lower. However, the ability in this culture completely recovered when pH was adjusted to 7 or the phosphate concentration was increased to the basal level. Analysis by denaturing gradient gel electrophoresis (DGGE) showed the whole population of the consortium became faint at low pH or low phosphate concentrations but became distinct again as much as those under the basal conditions, indicating that the decrease in the degradation ability caused by low pH was due to that whole population of the consortium underwent serious damage but could survive and recover. These results suggest the immobilized consortium on loofa sponge is a promising material for bioremediation of polluted water with these pesticides in paddy fields.

Biodegradation of crude oil across a wide range of salinities by an extremely halotolerant bacterial consortium MPD-M, immobilized onto polypropylene fibers

The bacterial consortium MPD-M, isolated from sediment associated with Colombian mangrove roots, was effective in the treatment of hydrocarbons in water with salinities varying from 0 to 180 g L(-1). Where the salinity of the culture medium surpassed 20 g L(-1), its effectiveness increased when the cells were immobilized on polypropylene fibers. Over the range of salinity evaluated, the immobilized cells significantly enhanced the biodegradation rate of crude oil compared with free-living cells, especially with increasing salinity in the culture medium. Contrary to that observed in free cell systems, the bacterial consortium MPD-M was highly stable in immobilized systems and it was not greatly affected by increments in salinity. Biodegradation was evident even at the highest salinity evaluated (180 g L(-1)), where biodegradation was between 4 and 7 times higher with immobilized cells compared to free cells. The biodegradation of pristane (PR) and phytane (PH) and of the aromatic fraction was also increased using cells immobilized on polypropylene fibers.

Scale up of fuel ethanol production from sugar beet juice using loofa sponge immobilized bioreactor

Production of fuel ethanol from sugar beet juice, using cells immobilized on loofa sponge was investigated. Based on ethanol productivity and ease of cell immobilization, a flocculating yeast strain, Saccharomyces cerevisiae IR2 was selected for ethanol production from sugar beet juice. It was found that raw sugar beet juice was an optimal substrate for ethanol production, requiring neither pH adjustment nor nitrogen source supplement. When compared with a 2 l bubble column bioreactor, mixing was not sufficient in an 8 l bioreactor containing a bed of sliced loofa sponges and consequently, the immobilized cells were not uniformly distributed within the bed. Most of the cells were immobilized in the lower part of the bed and this resulted in decreased ethanol productivity. By using an external loop bioreactor, constructing the fixed bed with cylindrical loofa sponges, dividing the bed into upper, middle and lower sections with approximately 1 cm spaces between them and circulating the broth through the loop during the immobilization, uniform cell distribution within the bed was achieved. Using this method, the system was scaled up to 50 l and when compared with the 2 l bubble column bioreactor, there were no significant differences (P > 0.05) in ethanol productivity and yield. By using external loop bioreactor to immobilize the cells uniformly on the loofa sponge beds, efficient large scale ethanol production systems can be constructed.