Liquid State Bioconversion Research Articles

Exploration of low-cost agro-industrial waste substrate for cellulase and xylanase production using Aspergillus heteromorphus

The current study was executed to explore the nutritive potential of low-cost agro-industrial waste substrates including anaerobically treated distillery spent wash (ADSW) and rice straw (RS) for enzyme production (cellulase and xylanase). The statistical model, Box–Behnken Design (BBD), was utilized to optimize the enzyme production through Aspergillus heteromorphus under liquid state bioconversion on examining the interactive interaction between substrate (ADSW), co-substrate (RS), temperature and initial pH. The BBD results revealed that the optimum levels of different factors for enzymes production were 6% ADSW, 3% RS, pH 5 and temperature 32.5 °C. The highest exoglucanase, xylanase and endoglucanase enzyme activities under optimum conditions were 6.3 IU/mL, 11.6 IU/mL and 8.1 IU/mL, respectively. The results confined that the agro-industrial waste substrate could be a cost-effective and eco-friendly alternative to produce value-added products like enzymes.

Liquid state bioconversion continuous bioreactor of sewage sludge treatment: Determination and evaluation of mixed fungi growth kinetics

Abstract Liquid state bioconversion (LSB), a bioremediation and biodewatering process was applied for sewage sludge treatment in this study. The LSB process is a non-hazardous, safer and environmentally friendlier method for ultimate sludge management and disposal compared to the other available technologies. The system presented in this study was developed by using mixed fungi of Aspergillus niger and Penicillium corylophilum to treat sewage sludge in a LSB bioreactor. This research was conducted in order to study the LSB process on continuous system in terms of kinetic coefficients determination. For the continuous LSB process, a mathematical model was developed from the basic principles of material balance based on Monod equation. By investigating the kinetics of substrate utilisation and biomass growth, the kinetic coefficients of growth yield coefficient (Y), specific microorganism decay rate (Kd), half saturation constant (Ks) and maximum specific growth rate (μmax) were found to be 0.79 g VSS g COD−1, 0.012 day−1, 1.78 g COD L−1 and 0.357 day−1, respectively.

Optimization of process parameters for pilot-scale liquid-state bioconversion of sewage sludge by mixed fungal inoculation

Liquid-state bioconversion (LSB) technique has great potential for application in bioremediation of sewage sludge. The purpose of this study is to determine the optimum level of LSB process of sewage sludge treatment by mixed fungal (Aspergillus niger and Penicillium corylophilum) inoculation in a pilot-scale bioreactor. The optimization of process factors was investigated using response surface methodology based on Box–Behnken design considering hydraulic retention time (HRT) and substrate influent concentration (S0) on nine responses for optimizing and fitted to the regression model. The optimum region was successfully depicted by optimized conditions, which was identified as the best fit for convenient multiple responses. The results from process verification were in close agreement with those obtained through predictions. Considering five runs of different conditions of HRT (low, medium and high 3.62, 6.13 and 8.27 days, respectively) with the range of S0 value (the highest 12.56 and the lowest 7.85 g L−1), it was monitored as the lower HRT was considered as the best option because it required minimum days of treatment than the others with influent concentration around 10 g L−1. Therefore, optimum process factors of 3.62 days for HRT and 10.12 g L−1 for S0 were identified as the best fit for LSB process and its performance was deviated by less than 5% in most of the cases compared to the predicted values. The recorded optimized results address a dynamic development in commercial-scale biological treatment of wastewater for safe and environment-friendly disposal in near future.

Pilot-scale production of lipase using palm oil mill effluent as a basal medium and its immobilization by selected materials.

A pilot-scale production of lipase using palm oil mill effluent (POME) as a fermentation basal medium was carried out, and parameters for immobilization of the produced lipase were optimized. Lipase production in a 300-L bioreactor was performed using two proposed strategies, constant power per volume (P/V) and constant tip speed. Moreover, lipase immobilization on different materials was also investigated. Lipase production was performed using liquid-state bioconversion of POME as the medium and Candida cylindracea as the inoculum. The fermentation medium was composed of 1% total suspended solids (TSS) of POME, 0.5% (w/v) peptone, 0.7% (v/v) Tween-80, and 2.2% inoculum. The medium composition was decided on the basis of the medium optimization results of a previous study. The fermentation was carried out for 48 h at 30°C and pH 6. The maximum lipase production was 5.72U/mL and 21.34 U/mL, obtained from the scale-up strategies of constant tip speed and P/V, respectively. Four accessible support materials were screened for their potential use in immobilization. The most suitable support material was found to be activated carbon, with a maximum immobilization of 94%.

Assessment of sewage sludge bioremediation at different hydraulic retention times using mixed fungal inoculation by liquid-state bioconversion

Sustainable, environmental friendly, and safe disposal of sewage treatment plant (STP) sludge is a global expectation. Bioremediation performance was examined at different hydraulic retention times (HRT) in 3-10 days and organic loading rates (OLR) at 0.66-7.81 g chemical oxygen demand (COD) per liter per day, with mixed filamentous fungal (Aspergillus niger and Penicillium corylophilum) inoculation by liquid-state bioconversion (LSB) technique as a continuous process in large-scale bioreactor. Encouraging results were monitored in treated sludge by LSB continuous process. The highest removal of total suspended solid (TSS), turbidity, and COD were achieved at 98, 99, and 93%, respectively, at 10 days HRT compared to control. The minimum volatile suspended solid/suspended solid implies the quality of water, which was recorded 0.59 at 10 days and 0.72 at 3 days of HRT. In treated supernatant with 88% protein removal at 10 days of HRT indicates a higher magnitude of purification of treated sludge. The specific resistance to filtration (SRF) quantifies the performance of dewaterability; it was recorded minimum 0.049 × 10(12) m kg(-1) at 10 days of HRT, which was equivalent to 97% decrease of SRF. The lower OLR and higher HRT directly influenced the bioremediation and dewaterability of STP sludge in LSB process. The obtained findings imply encouraging message in continuing treatment of STP sludge, i.e., bioremediation of wastewater for environmental friendly disposal in near future.

Optimization of process parameters for the production of citric acid using sewage sludge as major fermentation media

A research was conducted on liquid state bioconversion for the production of citric acid using sewage treatment plant (STP) sludge as the main substrate with supplementation of sucrose as co-substrate. Three parameters were examined to determine the best process optimization conducted in two liter (2 L) bioreactor. Two level factorial designs with three parameters were applied for the fermentation. It was carried out using local isolates of Aspergillus niger strain O103A at room temperature (30 to 32°C), agitation was set at three different values which are 100, 200 and 300 rpm. Initial pH for fermentation was set at 5 and it was further adjusted to three levels which are 2, 3 and 4 on the second day of the fermentation. Another parameter was aeration where 1, 1.5 and 2 vvm were introduced. The fermentation was carried out for five days. The maximum yield of citric acid obtained throughout the fermentation was 23.68 g/L, which is due to low pH, low agitation and high aeration values. Key words: Sewage treatment plant (STP) sludge, citric acid, Aspergillus niger, pH, aeration, agitation, two level factorial design

Statistical Optimization of Fermentation Conditions for Cellulase Production from Palm Oil Mill Effluent

Problem statement: Palm oil mill effluent discharged by the oil palm industries is considered as the mixed of high polluted effluent which is abundant (about 20 million tonnes year-1) and its effect contributes to the serious environmental problems through the pollution of water bodies. Approach: The aim of this study was to identify the potential of low cost substrate such as Palm Oil Mill Effluent (POME) for the production of cellulase enzyme by liquid state bioconversion. The filamentous fungus Trichoderma harzianum was used for liquid state bioconversion of POME for cellulase production. Statistical optimization was carried out to evaluate the physico-chemical parameters (factors) for maximum cellulase production by 2-level fractional factorial design with six central points. The polynomial regression model was developed using the experimental data including the effects of linear, quadratic and interaction of the factors. The factors involved were substrate (POME) and co-substrate (wheat flour) concentrations, temperature, pH, inoculum and agitation. Results: Statistical analysis showed that the optimum conditions were: Temperature of 30°C, substrate concentration of 2%, wheat flour concentration of 3%, pH of 4, inoculum of 3% and agitation of 200 rpm. Under these conditions, the model predicted the enzyme production to be about 14 FPU mL-1. Analysis Of Variance (ANOVA) of the design showed a high coefficient of determination (R2) value of 0.999, thus ensuring a high satisfactory adjustment of the quadratic model with the experimental data. Conclusion/Recommendations: This study indicates a better solution for waste management through the utilization of POME for cellulase production that could be used in the industrial applications such as bioethanol production.

Optimization of Media Composition for the Production of Bioprotein from Pineapple Skins by Liquid-State Bioconversion

Two-steps optimization strategy based on statistical experimental design was carried out to enhance bioprotein production by liquid state bioconversion utilizing pineapple skins as substrate. A two-level Plackett-Burman design was employed first where 11 variables were studied for their influence on bioprotein production. Pineapple Skins Soluble (PSS) sugar content, KH2PO4 and NH4H2PO4 were the most significant variables for improving bioprotein production. A three-level Central Composite Design (CCD) was employed for maximizing the bioprotein production. A mathematical model was developed to show the effects of each medium component and their combinatorial interaction on bioprotein production. The optimal medium composition for maximum bioprotein production was PSS content 1.0, KH2PO4 0.1 and NH4H2PO4 0.25. The final experiment was carried out to validate the model, which has shown to produce 514.2 g kg-1 bioprotein on the 5th day of fermentation with a slight increase of 0.02 from the experimental run in CCD. 2009 Asian Network for Scientific Information.

Statistical optimization of process conditions for cellulase production by liquid state bioconversion of domestic wastewater sludge

A two-level fractional factorial design (FFD) was used to determine the effects of six factors, i.e. substrate (domestic wastewater sludge – DWS) and co-substrate concentration (wheat flour – WF), temperature, initial pH, inoculum size and agitation rate on the production of cellulase enzyme by Trichoderma harzianum in liquid state bioconversion. On statistical analysis of the results from the experimental studies, optimum process conditions were found to be temperature 32.5 °C, substrate concentration (DWS) 0.75% (w/w), co-substrate (WF) concentration 2% (w/w), initial pH 5, inoculum size 2% (v/w) and agitation 175 rpm. Analysis of variance (ANOVA) showed a high coefficient of determination ( R 2) of 0.975. Cellulase activity reached 10.2 FPU/ml at day 3 during the fermentation process which indicated about 1.5-fold increase in production compared to the cellulase activity obtained from the results of design of experiment (6.9 FPU/ml). Biodegradation of DWS was also evaluated to verify the efficiency of the bioconversion process as a waste management method.

Potential Strain to Produce Bioprotein from Cheaper Carbon Source: Hope for Millions

Bioprotein production is one of the most promising breakthroughs of biotechnological innovations. Due to its increasing demand, the efficient strains, substrate and method must be used for high yield product. In this study, screening of five different cerivisiea, Mucor hiemalis and Thricoderma harzianum, was done for bioprotein production by liquid state bioconversion of wheat flour as a cheaper carbon source. Bioconversion was done with fixed wheat flour concentration of 2% (w/v) at a temperature 27°C, agitation of 150 rpm with 2% inoculum (106 spores mL-1). Biomass production was recorded continuously for six days and the protein content was also determined every day. From the observed results, Mucor hiemalis was found to be the most potential strain with biomass of about 11.48 g L-1 on the fourth day of treatment. With this promising result, the amount of bioprotein was further increased to 21.89 g L-1 by optimizing few process factors. Further optimization developments are in progress. This study may provide a better alternative in agricultural products by converting cheaper carbon source to valuable and quality product bioprotein, which can be used as supplement and additive in the animal feed and food as well as in chemical and pharmaceutical industries.

Treatment and Biodegradation Kinetics of Microbially Treated Domestic Wastewater Sludge

A laboratory-scale study was undertaken to evaluate the liquid state bioconversion (LSB) in terms of biodegradation of microbially treated domestic wastewater sludge (biosolids) as well as its kinetics. The potential fungal strains and process factors developed from previous studies were used throughout the study. The results presented in this study showed that an effective biodegradation occurred with the biosolids (sludge cake) accumulated. The maximum biosolids (sludge cake) accumulated (93.8 g/kg of liquid sludge) enriched with the biomass protein (30.2 g/kg of dry biosolids), was achieved which improved the effluent quality by enhancing the removal of chemical oxygen demand (COD), reducing sugar (RS), soluble protein (SP), total dissolved solids (TDS), and total suspended solids (TSS). The higher reduction of specific resistance to filtration (SRF) was observed during bioconversion process. The kinetics results showed that the experimental data were better fitted for the biodegradation efficiency, and biosolids accumulation and biodegradation rate.

Liquid State Bioconversion of Sewage Treatment Plant Sludge in Batch Fermenter and Shake Flask

Liquid State Bioconversion of Sewage Treatment Plant Sludge in Batch Fermenter and Shake Flask

Liquid State Bioconversion of Sewage Treatment Plant Sludge in Batch Fermenter and Shake Flask

A study on liquid state bioconversion of sewage treatment plant (STP) sludge was assisted to evaluate the performance of batch fermenter compared to shake flask in a laboratory. Bioconversion of STP sludge was highly influenced by the mixed fungal culture of Penicillium corylophilum and Aspergillus niger after 4 days of treatment. The results showed that about 24.9 g kg(-1) dry sludge cake (DSC) was produced with enrichment of fungal biomass protein in fermenter while 20.1 g kg(-1) in shake flask after 4 days of fungal treatment. The effective biodegradation of STP sludge was recorded in both fermenter and shake flask experiment compared to control (uninnoculated sample). The results presented in this study revealed that the overall performance of fermenter in terms of sludge cake (biosolids) accumulation and biodegradation of STP sludge was higher than the shake flask.

Optimization of liquid state bioconversion process for microbial treatment of domestic wastewater sludge

The evaluation of cheap carbon sources (co-substrate) and process conditions for microbial treatment of domestic wastewater sludge (DWS) was investigated using a liquid state bioconversion (LSB) laboratory scale process. Six cheap carbon sources were used: wheat flour (WF), rice flour (RF), corn flour (CF), sago starch (SS), cassava starch (CS), and commercial sugar (S). Process conditions such as co-substrate(s) concentration, temperature, initial pH, and inoculum size were optimized in terms of dry filter cake (DFC) production, removal of total suspended solids (TSS), turbidity (optical density against distilled water, 660 nm), and chemical oxygen demand (COD) in supernatant. The results obtained indicated that sludge containing wheat flour as a carbon source was a better co-substrate for microbial growth, with significant utilization for minimizing the dissolved and suspended materials in sludge. The optimized parameters for fungal treatment of DWS obtained were 1.5–2% (w/w) of WF concentration, temperature of 33–35°C, initial pH of 4.5–5.5, and inoculum size of 2–3% v/w. Effective results for optimum values were recoded at 4 d of microbial treatment.Key words: liquid state bioconversion, domestic wastewater sludge, process conditions, cheap carbon sources, microbial treatment.

Biosolids accumulation and biodegradation of domestic wastewater treatment plant sludge by developed liquid state bioconversion process using a batch fermenter

The biosolids accumulation and biodegradation of domestic wastewater treatment plant (DWTP) sludge by filamentous fungi have been investigated in a batch fermenter. The filamentous fungi Aspergillus niger and Penicillium corylophilum isolated from wastewater and DWTP sludge was used to evaluate the treatment performance. The optimized mixed inoculum ( A. niger and P. corylophilum) and developed process conditions (co-substrate and its concentration, temperature, initial pH, inoculum size, and aeration and agitaion rate) were incorporated to accelerate the DWTP sludge treatment process. The results showed that microbial treatment of higher strength of DWTP sludge (4% w/w of TSS) was highly influenced by the liquid state bioconversion (LSB) process. In developed bioconversion processes, 93.8 g/kg of biosolids was enriched with fungal biomass protein of 30 g/kg. Enrichment of nutrients such as nitrogen (N), phosphorous (P), potassium (K) in biosolids was recorded in 6.2% (w/w), 3.1% (w/w) and 0.15% (w/w) from its initial values of 4.8% (w/w), 2.0% (w/w) and 0.08% (w/w) respectively after 10 days of fungal treatment. The biodegradation results revealed that 98.8% of TSS, 98.2% of TDS, 97.3% of turbidity, 80.2% of soluble protein, 98.8% of reducing sugar and 92.7% of COD in treated DWTP sludge supernatant were removed after 8 days of microbial treatment. The specific resistance to filtration (SRF) in treated sludge (1.4×10 12 m/kg) was decreased tremendously by the microbial treatment of DWTP sludge after 6 days of fermentation compared to untreated sample (85×10 12 m/kg).

Enhanced settleability and dewaterability of fungal treated domestic wastewater sludge by liquid state bioconversion process

A study was conducted to evaluate the settleability and dewaterability of fungal treated and untreated sludge using liquid state bioconversion process. The fungal mixed culture of Aspergillus niger and Penicillium corylophilum was used for fungal pretreatment of wastewater sludge. The fungal strains immobilized/entrapped on sludge particles with the formation of pellets and enhanced the separation process. The results presented in this study showed that the sludge particles (pellets) size of 2–5 mm of diameter were formed with the microbial treatment of sludge after 2 days of fermentation that contained maximum 33.7% of total particles with 3–3.5 mm of diameter. The settling rate (measured as total suspended solids (TSS) concentration, 130 mg/l) was faster in treated sludge than untreated sludge (TSS concentration, 440 mg/l) after 1 min of settling time. In 1 min of settling operation, 86.45% of TSS was settled in treated sludge while 4.35% of TSS settled in raw sludge. Lower turbidity was observed in treated sludge as compared to untreated sludge. The results to specific resistance to filtration (SRF) revealed that the fungal inoculum had significant potentiality to reduce SRF by 99.8% and 98.7% for 1% w/w and 4% w/w of TSS sludge, respectively. The optimum fermentation period recorded was 3 days for 1% w/w sludge and 6 days for 4% w/w sludge, respectively, for dewaterability test.

Optimization of Compatible Mixed Cultures for Liquid State Bioconversion of Municipal Wastewater Sludge

The filamentous fungal strains such as Penicillium corylophilum (P), Aspergillus niger (A), Trichoderma harzianum (T) and Phanerochaete chrysosporium (PC) isolated from its relevant sources (wastewater, sewage sludge and sludge cake) were selected for compatible/incompatible mixed cultures. Six combinations of P. corylophilum and A. niger (P/A); P. corylophilum and P. chrysosporium (P/PC); P. corylophilum and T. harzianum (P/T); A. niger and T. harzianum (A/T); A. niger and P. chrysosporium (A/PC); T. harzianum and P. chrysosporium (T/PC) were used to evaluate their potential performance as compatible/incompatible mixed culture for the treatment of municipal wastewater sludge in a bioconversion process. The results of the present study showed that the combinations of P/A, P/PC and A/PC showed compatible growth and the rest of the combinations (P/T, A/T and T/PC) were incompatible cultures. A maximum production of dry biomass and dry filter cake were recorded in the compatible mixed culture of P. corylophilum and A. niger (P/A). A maximum reduction of COD (90%) and a decreased filtration time of treated sludge was observed in the case of P/A microbial mixed culture. The pH value was also affected by the fungal cultures. Effective results were observed by using microbial mixed culture after four days of treatment compared to other treatments (2 and 6 days).

DOMESTIC WASTEWATER BIOSOLIDS ACCUMULATION BY LIQUID STATE BIOCONVERSION PROCESS FOR RAPID COMPOSTING

ABSTRACT Bioconversion of higher strength of domestic wastewater biosolids (sludge) (4% w/w of TSS) by mixed fungal culture of Aspergillus niger and Penicillium corylophilum was studied in a laboratory. The effect of potential mixed fungi on domestic wastewater sludge accelerated the liquid state bioconversion (LSB) process. The highest production of dry sludge cake (biosolids) was enriched with fungal biomass to about 85.66 g/kg containing 25.23 g/kg of protein after 8 days of treatment. The results presented in this study revealed that the reduction of chemical oxygen demand (COD), total suspended solid (TSS), and specific resistance to filtration (SRF) of treated sludge were highly influenced by the fungal culture as compared to control (uninnoculated). The maximum removal rates in treated sludge (biosolids) supernatant recorded were 92% of COD and 98.8% of TSS. Lower SRF (1.08 × 1012 m/kg) was perceived in microbially treated sludge after 6 days of fermentation. The observed parameters were highly influenced after 8 days of treatment. The influence of pH was also studied and presented in the paper.

EFFECT OF AGITATION AND AERATION ON BIOCONVERSION OF DOMESTIC WASTEWATER SLUDGE IN A BATCH FERMENTER

ABSTRACT Effects of agitation and aeration rate on microbial treatment of domestic wastewater sludge were investigated in a batch fermenter using mixed culture of Penicillium corylophilum and Aspergillus niger. It was found that liquid state bioconversion (LSB) of wastewater sludge was highly influenced by the effects of agitation and aeration. The maximum production of sludge cake and reduction of organic substances in treated sludge were recorded at 150–200 rpm of agitation speed and 0.5 vvm of aeration rate after 72 h of treatment. No effective results were observed at higher rate of agitation (300 rpm) and aeration (1.5 vvm) as compared to optimum values. The results showed that the minimum level of air saturation (pO2) was adequate to maintain the bioconversion process.

FILAMENTOUS FUNGI IN INDAH WATER KONSORTIUM (IWK) SEWAGE TREATMENT PLANT FOR BIOLOGICAL TREATMENT OF DOMESTIC WASTEWATER SLUDGE

ABSTRACT A study was carried out to isolate and identify filamentous fungi for the treatment of domestic wastewater sludge by enhancing biodegradability, settleability and dewaterability of treated sludge using liquid state bioconversion process. A total of 70 strains of filamentous fungi were isolated from three different sources (wastewater, sewage sludge and leachate) of IWK's (Indah Water Konsortium) sewage treatment plant, Malaysia. The isolated strains were purified by conventional techniques and identified by microscopic examination. The strains isolated belonged to the genera of Penicillium, Aspergillus, Trichoderma, Spicaria and Hyaloflorae The distribution of observed isolated fungi were 41% in sewage sludge followed by 39% in wastewater and 20% in leachate. The predominant fungus was Penicillium (39 strains). The second and third most common isolates were Aspergillus (14 strains) and Trichoderma (12 strains). The other isolates were Spicaria (3 strains) and Hyaloflorae (2 strains). Three strains (WWZP1003, LZP3001, LZP3005) of Penicillium (P. corylophilum, P. waksmanii, and P. citrinum respectively), 2 strains (WWZA1006 and SS2017) of Aspergillus (A. terrues and A. flavus respectively) and one strain (SSZT2008) of Trichoderma (T. harzianum) were tentatively identified up to species level and finally verified by CABI Bioscience Identification Services, UK.