Inoculum Ratio Research Articles

Kinetic prediction of biochemical methane potential of pig slurry

Empirical Kinetic Models have been used to describe and establish the Anaerobic Digestion kinetics of pig slurry’s (8% TS) Biochemical Chemical Potential. A wide selection of Empirical Kinetic Models were fitted to the experimental data collected in batch assays of different Substrate to Inoculum ratios, 0.65 (BMP1) and 1 (BMP2). For the selection of the most suitable model for each BMP assay, the statistical tools R2 and the RMSE, along with the Information Criterion AIC and BIC, were taken into consideration. From all the studied models, the Weibull model proved to be the most suitable for kinetic parameter prediction for both BMP1 and BMP2 assays. This model presented the lowest values of AIC and BIC, along with the highest value of R2 and the lowest RMSE. In this regard, a R2=0.998, and a RMSE=0.004, was obtained for BMP1, and a R2=0.999 and a RMSE=0.008 for BMP2.

Bacillus subtilis BS-15 Effectively Improves Plantaricin Production and the Regulatory Biosynthesis in Lactiplantibacillus plantarum RX-8.

Plantaricin is a broad-spectrum bacteriocin produced by Lactiplantibacillus plantarum with significant food industry application potential. It was found that the plantaricin production of L. plantarum RX-8 was enhanced when co-culturing with Bacillus subtilis BS-15. This study, therefore, set out to explore how B. subtilis BS-15 induces biosynthesis of plantaricin. The effect of co-culturing with B. subtilis BS-15 on cell growth, plantaricin production, quorum-sensing (QS) signal molecule PlnA/autoinducer-2 (AI-2) secretion, as well as plantaricin biosynthesis gene cluster and AI-2 synthesis-associated gene expression, was investigated in bacteriocin-producer L. plantarum RX-8. When L. plantarum RX-8 and B. subtilis BS-15 were co-inoculated in Man–Rogosa–Sharp (MRS) for 20 h at an inoculum ratio of 1:1 (106:106 CFU/ml), the greatest plantaricin output (2,048 AU/ml) was obtained, rising by 32-fold compared with the monoculture of L. plantarum RX-8. Additionally, co-culture increased PlnA-inducing activity and AI-2 activity by 8- and 1.14-fold, respectively, over monoculture. RT-qPCR findings generated every 4 h (4–32 h) demonstrated that B. subtilis BS-15 remarkably improved the transcription of plnABCD and plnEF, and increased pfs and luxS transcription, even when using 200 mM D-ribose, a kind of AI-2 inhibitor. Based on the above findings, co-culturing with B. subtilis BS-15 as an environmental stimulus could activate the plantaricin induction via the PlnA-mediated intraspecies QS system and the AI-2-mediated interspecies QS system. Moreover, the inducing effect of PlnA and AI-2 in co-culture was independent. Differential proteomics analysis of B. subtilis BS-15 in co-culture indicated that bacteriocin-inducing regulatory mechanism may be related to flagellar assembly, peptidoglycan biosynthesis, anaerobic respiration, glycine cleavage system, or thiamin pyrophosphate biosynthesis.

Bacterial Core Flooding on Limestone Artificial Core for Microbial Enhanced Oil Recovery (MEOR) Application

Microbial Enhanced Oil Recovery (MEOR) is a tertiary methods to increase oil production using bioproduct of microorganisms form acidic compounds, gases, polymers, and surfactants, as an agent that can alter the characteristics of the reservoir rock and oil. Previous laboratory research indicated that bacterial isolates indigen from petroleum reservoir, MSD4 and MSD5, with the amount of inoculum ratio 1:1 in recovery medium can reduce the viscosity value and interfacial tension of oil. The aim of this research was to determine the amount of oil recovery from low saturated oil in limestone artificial core by using bacterial core flooding method, also to determine the physical character and chemical character changes in limestone rocks and petroleum. Each bacteria, MSD4 and MSD5, were adapted to the medium SMSS that have been added by 5% oil. Inoculum of indigen bacterial cultures to be injected into the limestone core was bred in the SMSS culture medium added molasses with a varied amount, as much as 1%, 2%, and 3%. From the those variation, the amount of molasses added as much as 1% in the medium SMSS, is known that MSD4 and MSD5 cultures can grow to the highest μ respectively at the age of 16-hour and 24-hour with a value at 0.9992 hours-1 and 0, 9993 hours-1. Inoculum MSD4 and MSD5 cultures with the amount of 1:1 ratio and each bacterial cell density 107-108 cells/mL, were injected into artificial limestone cores with oil saturated less than 15%. The value of rock porosity range used for the simulation of bacterial flooding is 37% -42%, while permeability range used low permeability value (1mD-10mD) and fair permeability value (10mD-50mD). High oil recovery factor (RF%) were obtained from bacterial flooding simulation and incubated for 7 days in a temperature of 55°C on medium SMSS for cores with low permeability values and fair, has a range of 16,3% - 32% and 12% -15,3%. The result of microorganisms activity in limestone rocks from a change on physical character, have a range at -41,8% - 698% on permeability value and a range at -63,85% - 1,03% on porosity value. Indicator of bacterial attachment on limestone cores can be determined by photomicrographs analyzing Scanning Electron Microscope and Energy Dispersive X-ray Spectroscopy.

Effect of the Substrate to Inoculum Ratios on the Kinetics of Biogas Production during the Mesophilic Anaerobic Digestion of Food Waste

This study evaluates the effects of the varying substrate to inoculum ratios (S:I) of 0.5, 1, 2, 3, 4, 5, and 6 (volatile solids/VS basis) on the kinetics of biogas production during batch mesophilic (35 ± 1 °C) anaerobic digestion (AD) of simulated food waste (FW), using anaerobic digestate as the inoculum. Kinetic parameters during biogas production (scrubbed with NaOH solution) are predicted by the first-order and the modified Gompertz model. The observed average specific biogas yields are in descending order corresponding to the S:I ratios 1, 2, 4, 6, 3, 5, and 0.5, respectively, and the significant effect of the S:I ratio was observed. The tests with the S:I of 1 have the maximum average biogas production rates of 88.56 NmL/gVS.d, whereas tests with the S:I of 6 exhibited the lowest production rates (24.61 NmL/gVS.d). The maximum biogas yields, predicted by the first order and the modified Gompertz model, are 668.65 NmL/gVS (experimental 674.40 ± 29.10 NmL/gVS) and 653.17 NmL/gVS, respectively. The modified Gompertz model has been proven to be suitable in predicting biogas production from FW. VS removal efficiency is greater in higher S:I ratios, with a maximum of 78.80 % at the S:I ratio of 6, supported by the longer incubation time. Moreover, a significant effect of the S:I ratio is seen on kinetics and energy recovery from the AD of FW.

A novel co-cultivation strategy to generate low-crystallinity bacterial cellulose and increase nisin yields

In this study, a co-culturing Enterobacter sp. and Lactococcus lactis strategy was developed to alter bacterial cellulose (BC) properties and increase nisin yields. We generated high nisin yields (6260 IU/mL) by altering inoculum ratios and inoculation times in a novel co-culture system. Critically, these were 85% higher than L. lactis monocultures. By monitoring fermentation broth pH and lactic acid yields, the pH was higher and lactic acid yields lower during co-culture conditions when compared with L. lactis monocultures, suggesting that co-culturing was more suitable for L. lactis nisin production. We also determined BC film yields and properties (BC, BC-N, and BC-N after nisin release). BC yields produced by co-culturing were not very different from Enterobacter sp. monocultures, but crystallinity was significantly altered. Collectively, our co-culture system adequately and economically modified BC fibers by interfering with self-assembly and crystallization processes during BC synthesis, with significantly improved nisin yields.

Life cycle assessment and life cycle costing of advanced anaerobic digestion of organic fraction municipal solid waste

The aim of this study is the evaluation of the environmental sustainability by means of Life Cycle Assessment (LCA) and economic profitability through Life Cycle Costing (LCC) of the 18 anaerobic digestion (AD) configurations carried out on Organic Fraction Municipal Solid Waste (OFMSW) at three Substrate Inoculum (S:I) ratios (1:2, 1:1 and 2:1) for three different inoculum incubation times (0, 5 and 10 d). The adopted approach was the eco-efficiency perspective, coming from the combination of technical, environmental (LCA) and economic (LCC) perspectives. The main findings of the study were that increasing both the S:I ratio and the inoculum incubation time (5 and 10 d) the environmental impacts decreased, and economic profitability increased. The lowest values of Climate Change were achieved by the AD performed with both inocula WAS and CAS for 10 d at S:I equal to 2:1: 28.67 and 27.72 kg CO2 eq respectively. The minimum AD plant size for which all the 18 AD configurations was economically profitable after 5 y of amortization was 30,000 t/y of OFMSW. Capital and operational costs decreased by increasing the incubation time of the inoculum and the S:I ratio, since higher specific biogas rate was reached, and smaller AD bio-reactor volume were adopted because hydraulic retention time decreased.The AD plant size, for which maximal revenues and minimal capital and operational costs were detected, was 50,000 t/y OFMSW. Among all the AD configurations, the environmental sustainability and economic profitability were reached by test perfomed with inocula WAS and CAS incubated for 5 and 10 d at the highest S:I ratio 2:1.

Effects of organic loading rate on methane production from switchgrass in batch and semi-continuous stirred tank reactor system

Long-term anaerobic digestion of switchgrass (SG) was investigated in batch and semi-continuous reactors operating at different Substrate to Inoculum (S:I) ratios and organic loading rates (OLRs) by monitoring process stability, microbial community structure, and investigating kinetic modeling. The highest methane yield of 204 mLCH4/gVS was observed when the batch system was operated at the S:I ratio of 1.1. Methane yields in the semi-continuous configuration were around 148, 157, and 60 mLCH4/gVS at OLRs of 0.75, 1.0, and 1.5 gVS/(L.d), respectively. A drastic decrease in methane yields was observed at the highest OLR value of 1.5 gVS/(L.d). The optimum OLR in the semi-continuous configuration was decided as 1.0 gVS/(L.d) where 35% of the SG theoretical methane yield and 38% energy recovery were attained. Several methanogenic archaea, Methanosarcina, Methanosaeta, Methanothrix, and Methanomethylovorans, together with bacteria species, Chloroflexi, Firmicutes, Spirochaetes, and Actinobacteria were observed in the semi-continuous configuration after 270 days of operation. The dominant bacterial phyla of s-CSTR were mostly members of Spirochaetes phylum, which plays a considerable role in acetate oxidation under either mesophilic or thermophilic conditions.

Acidogenic phase anaerobic digestion of pretreated sugarcane filter cake for co-digestion with biogas effluent to enhance the methane production

This study aimed to evaluate the possibility of acidogenic phase as the pretreatment method of filter cake (FC) before being co-digested with biogas effluent (BE), and anaerobic sludge (AS) for methane production. The effects of separation of acidogenic and methanogenic phases on the improvement of the methane production process from a co-digestion of FC with BE, and AS were also investigated. FC was pretreated through acidogenic phase anaerobic digestion (AD) using a different substrate to inoculum ratios (SIRs) and substrate concentrations. The optimum conditions for acidogenic phase AD of FC were SIRs of 4:1 and substrate concentration of 15.0% total solid (TS). Resultantly, the maximum volatile fatty acids (VFA) yield of 0.17 g-VFAs/g-VS (volatile solids) was obtained. The major VFA components were butyric and acetic acid. The acidogenic phase of FC was semi-continuously conducted in a continuous stirred tank reactor (CSTR) at various hydraulic retention time (HRT). The highest concentration and yield of VFAs of 7.29 g/L and 0.39 g-VFAs/g-VS, respectively, were observed at HRT of 5 d. The major VFAs observed were butyric acid (48.8%), and acetic acid (36.8%). Subsequently, the proportions of pretreated FC, BE, and AS to produce methane were optimized in batch experiments. The highest methane yield (MY) of 195.9 mL-CH4/g-VS was achieved at the proportions of pretreated FC and BE of 37.75 and 22.25 g-VS/L, respectively, without the addition of AS. The optimum substrate proportion was further used to determine the MY in a 10 L CSTR with the various HRT. The maximum MY of 130.5 mL-CH4/g-VS was achieved at an HRT of 20 d which produced an EY of 4.7 kJ/g-VS. Analysis of microbial community by 16S rRNA amplicon sequencing on an illumination platform indicated that genera Rummeliibacillus, Lactobacillus, and Bacillus were the dominant bacteria found in the acidogenic phase. Methanoculleus and Methanosarcina were found to be the most dominant genera in methane fermentation. Results suggested that acidogenic phase digestion can be used as an alternative method for FC pretreatment to improve methane production. Furthermore, the separation of acidogenic and methanogenic phases improves the process stability.

Optimization of Biomethane Production via Fermentation of Chicken Manure Using Marine Sediment: A Modeling Approach Using Response Surface Methodology

In this study, marine sediment (MS) was successfully used as a source of methanogenic bacteria for the anaerobic digestion (AD) of chicken manure (CM). Using MS showed high production in liquid and semi-solid conditions. Even in solid conditions, 169.3 mL/g volatile solids of chicken manure (VS-CM) was produced, despite the accumulation of ammonia (4.2 g NH3-N/kg CM). To the best of our knowledge, this is the highest methane production from CM alone, without pretreatment, in solid conditions (20%). Comparing MS to Ozouh sludge (excess activated sewage sludge) (OS), using OS under semi-solid conditions resulted in higher methane production, while using MS resulted in more ammonia tolerance (301 mL/gVS-CM at 8.58 g NH3-N/kg). Production optimization was carried out via a response surface methodology (RDM) model involving four independent variables (inoculum ratio, total solid content, NaCl concentration, and incubation time). Optimized methane production (324.36 mL/gVS-CM) was at a CM:MS ratio of 1:2.5 with no NaCl supplementation, 10% total solid content, and an incubation time of 45 days.

Process Simulation and Optimization of Anaerobic Co-Digestion

Anaerobic digestion (AD) is an established method that has been extensively utilized for waste management, waste treatment, and biogas production. Anaerobic co-digestion (AcoD) is regarded as a practical approach to address substrate characteristics and system optimization issues. The distinction between AcoD and mono-digestion is that AcoD has a higher organic loading and significant substrate composition variation. There are many factors involved in AcoD which affect the biogas plant’s production ability and performance. Using response surface methodology (RSM) to forecast the optimal conditions for maximum biogas output, this article provides an overview of the different operational parameters in the AcoD process, modeling of the AcoD process, and overall process optimization. Standard software used for AcoD process simulation are Aspen Plus, SuperPro Designer, BioWin, CFD, and MATLAB. Review addresses design, development, and optimization frameworks for biogas production systems that take numerous aspects into account. The most significant AcoD optimization parameters include temperature, co-substrate concentration, inoculum ratio (percent), and C/N ratio.

318 Enforced tumor specific MHC-I heterogeneity in triple negative breast cancer drives immunotherapy resistance

BackgroundDespite the broad success of immune checkpoint inhibition (ICI e.g. anti-Programmed Death Ligand-1 [PD-L1]) in cancer treatment, tumor-intrinsic factors leading to intrinsic and acquired resistance are poorly understood. Tumor specific MHC-I expression is indispensable for anti-PD-1/L1 response as complete loss of MHC-I via B2M deletion results in inability of CD8+ T cells to recognize tumor-associated antigens. However, MHC-I is heterogeneously downregulated or lost in many tumor types. Tumor cell destruction can also occur through non-synaptic mechanisms, in a so-called ‘field effect’. Therefore, we modeled heterogeneous loss of MHC-I expression in breast cancer and experimentally evaluated how heterogeneous MHC-I loss affects response to anti-PD-L1 therapy.MethodsWe performed quantitative immunofluorescence for MHC-I and Pan-CK on breast cancer tumors (n=410). To determine the functional effect of MHC-I heterogeneity on anti-PD-L1 response, we used an immunocompetent EMT6 orthotopic mammary tumor model which ubiquitously expresses MHC-I at baseline. Using CRISPR/Cas9, we engineered EMT6 cells with B2m loci excision resulting in complete knockout of MHC-I on the cell surface. We then orthotopically implanted B2m-comtetent and B2m-KO cells at varying inoculum ratios (100:0, 90:10, 50:50, 10:90, 0:100) into syngeneic Balb/C mice and assessed immune responsiveness and efficacy of checkpoint inhibition. Additionally, to look at how loss of MHC-I affects the tumor microenvironment we will use the PanCancer Immune NanoString panel (n=770 genes) to evaluate gene expression patterns in tumor cells and infiltrating immune cells.ResultsIn patient samples, we identified high diversity in MHC-I expression across all clinical subtypes, with triple negative breast cancer (TNBC) having the highest MHC-I expression. Chemotherapy-treated tumors had higher MHC-I levels than untreated tumors. In mice when 10% of cells were B2m-KO, we observed a 50% reduction in complete eradication of EMT6 tumors with aPD-L1 treatment and reduced disease-stabilization and no complete responses when a 50% mixture of MHC-I deficient cells. An increasing percentage of B2m KO leads to worse outcomes overall and a decrease in infiltrating T cells.ConclusionsOur work suggests that there is an ICI-responsive phenotype that is driven by heterogeneity in MHC-I expression levels. As little as 10% of tumor specific MHC-I loss can lead to therapeutic resistance and a decrease in complete responders. This represents that early TNBC may be less responsive to single-agent PD-L1 due to specific percentages of MHC-I loss. MHC-I expression can influence therapy outcomes and potentially lead to novel observations of how to overcome lack of, or limited, MHC-I expression.

Enhanced methane production and hydrocarbon removal from petroleum refinery sludge after Pseudomonas putida pretreatment and process scale-up

The influence of Pseudomonas putida 7525 strain on the pretreatment of petroleum refinery sludge was optimized at different dosages to maximize solubilization for improved biodegradability. Laccase-producing P. putida strain at a dosage of 108 CFU/mL resulted in 249% and 121.57% increments in soluble chemical oxygen demand and volatile fatty acids production respectively as compared to untreated within 6 days of incubation. 1L biochemical methane potential test conducted for optimization of different inoculum and pretreated substrate ratios (0.3, 0.4, 0.5, 0.7 and 1.0) revealed maximum methane augmentation (62%) and volatile solids degradation (66.7%) at ratio 0.5. Scaled-up study (20L) for ratio 0.5 resulted in 57.07% total petroleum hydrocarbon, 62.98% oil and grease and 91.9% phenol removal within 50 days of digestion of pretreated PS. Kinetic modelling of cumulative methane yield indicated that modified Gompertz model showed the best fit thereby, evincing the potency of bacterial species for bioremediation of PS.

Consolidated bioprocessing of paper sludge to acetic acid by clostridial co-culture

Thermophilic Clostridium thermocellum (CEL), Clostridium clariflavum (CLA) and Moorella thermoacetica (C. thermoaceticum, ACE) in co-culture were used to directly ferment paper sludge. The triculture system could greatly solubilize cellulose as well as hemicellulose and fermented them into acetic acid. Various microbial inoculum ratios were explored in 0.5-L fermenter and it was found that CEL to CLA to ACE inoculation volume ratio of 1:1:1 provided the highest product concentration and best efficiency. Scale-up to 5.0-L was carried out and resulted into 86.2% carbon conversion efficiency of all saccharides in paper sludge to acetic acid and 90.5% to total products. Such high efficiencies reached without pretreatment and without addition of expensive enzymes consist of a breakthrough towards cost-performant biorefinery. In addition, this work contributes to the yet limited knowledge on the combination of pure anaerobic bacterial cultures.

Bio-immobilization of soluble Mn(II) in aqueous solution with co-occurred Mn(II)-oxidizing bacteria: Facilitation or inhibition?

Mn(II)-oxidizing bacteria (MOB) can immobilize soluble Mn(II) to form biogenic Mn oxides (BioMnOx) which could be recovered as useful resources. In the present study, dual-species co-cultured systems of three MOB strains, Enterobacter sp. DS02Eh01 (D1), Bacillus sp. WSE02 (W2) and Staphylococcus sp. WLS01 (W1), were developed to explore the effects of co-occurrence on Mn(II) immobilization/oxidation. The results indicated that co-occurred bacteria were able to immobilize Mn(II), although there were interactions between them. Both initial volumetric inoculum ratios (IVIRs) and initial Mn(II) levels (IMLs) affected the Mn(II) immobilization/oxidation process. Under the same IVIR, the unique Mn tolerance of strain D1 was not inhibited, leading to its superior abundance in the co-cultured system. While strain W1 and W2, which had powerful Mn(II) immobilization ability in mono-culture, showed different responses to the presence of D1: strain W2 was still able to complete Mn(II) immobilization, while the Mn(II) immobilization ability of W1 was found to be down-regulated. The Mn(II) immobilization/oxidation capabilities of strain W1 and W2 were maintained or even surpassed the mono-cultures while they were co-occurred. The physicochemical properties of Mn(II) immobilization products (MIPs) were also varied in the co-cultured systems but the enzyme-based formation mechanisms of Mn(II) oxidation were not apparently affected by the co-occurrence. The results of this study help better understand the nature of the Mn biogeochemical cycle induced by co-occurred MOB species and guide the engineering application in the treatment/recovery of Mn(II)-laden wastewater.

Bioenergy Production through Mono and Co-Digestion of Tomato Residues

The agro-industry of tomato generates three types of residues: ripe rotten tomato (unfit for consumption) (RT), green (unripe) tomato (GT), and tomato branches including leaves and stems (TB). These materials are commonly wasted or used as feed for livestock. Energy production through anaerobic digestion is an alternative way to manage and simultaneously valorise these materials. Initially, the operating conditions of mono anaerobic digestion were investigated using RT. Thus, a design of experiments based on a two-level fractional factorial design with resolution V was performed to determine the factors that affect biochemical methane potential (BMP). The substrate to inoculum ratio (SIR), total volatile solids concentration (VSt), working volume (WV), presence of nutrients (Nu), and the pre-incubation of the inoculum (Inc) were investigated. The results showed that SIR is the most important factor. The maximum BMP for RT was 297 NmLCH4/gVS with SIR = 0.5; tVS = 20 g/L; WV = 20%; no pre-incubation and the presence of nutrients. Using these optimum operating conditions, co-digestion was investigated through a mixture design approach. The substrates RT and GT presented similar BMP values, whereas TB led to a significantly lower BMP. Indeed, when high concentrations of TB were used, a significant decrease in methane production was observed. Nonetheless, the highest BMP was achieved with a mixture of 63% RT + 20% GT + 17% TB, with a production of 324 NmLCH4/gVS, corresponding to a synergetic co-digestion performance index of about 1.20. In general, although the substrate RT generates the highest BMP, the mixture with GT did not impair the methane yield. Overall, the co-digestion of tomato residues must be conducted with SIR close to 0.5 and the content of tomato branches in the reaction mixture should be kept low (up to 20%).

Biochar amendment rapidly shifts microbial community structure with enhanced thermophilic digestion activity

Effects of powdered (<0.075 mm) biochar on thermophilic anaerobic digestion were investigated with biochemical methane potential (BMP) assays. The assays had substrate to inoculum ratios (SIR) of 2.2 and 4.4 g-volatile solids (VS)/g-VS and biochar dosing of 6 g/g-total solids (TS)inoculum. Compared to control, biochar amendment enhanced methane production rates by 94%, 75%, and 20% in assays utilizing substrates of acidified sludge at 70 °C, 55 °C and non-acidified mixed sludge, respectively. All controls experienced acute inhibition with lag phases from 12 − 52 days at SIR of 4.4 g-VS/g-VS, while assays with biochar generated methane from day 4. Biochar addition resulted in a rapid shift in microbial community structure associated with an increase in Methanothermobacteraeae (hydrogenotrophic) and Methanosarcinaceae archaea, as well as various volatile fatty acid (VFA)-degrading and hydrogen-producing bacteria. Biochar presents great potential to tackle VFA accumulation, abbreviate lag phase and increase methane rate, particularly at high organic loadings.

The power of two: An artificial microbial consortium for the conversion of inulin into Polyhydroxyalkanoates

One of the major issues for the microbial production of polyhydroxyalkanoates (PHA) is to secure renewable, non-food biomass feedstocks to feed the fermentation process. Inulin, a polydisperse fructan that accumulates as reserve polysaccharide in the roots of several low-requirement crops, has the potential to face this challenge.In this work, a “substrate facilitator” microbial consortium was designed to address PHA production using inulin as feedstock. A microbial collection of Bacillus species was screened for efficient inulinase producer and the genome of the selected strain, RHF15, identified as Bacillus gibsonii, was analysed unravelling its wide catabolic potential. RHF15 was co-cultured with Cupriavidus necator, an established PHA producer, lacking the ability to metabolize inulin. A Central Composite Rotary Design (CCRD) was applied to optimise PHA synthesis from inulin by the designed artificial microbial consortium, assessing the impact of species inoculum ratio and inulin and N-source concentrations. In the optimized conditions, a maximum of 1.9 g L−1 of Polyhydroxybutyrate (PHB), corresponding to ~80% (gpolymer/gCDW) polymer content was achieved. The investigated approach represents an effective process optimization method, potentially applicable to the production of PHA from other complex C- sources.

Optimization of electrokinetic pretreatment for enhanced methane production and toxicity reduction from petroleum refinery sludge

This study examined the effect of electrokinetic pretreatment on petroleum sludge (PS) released from the wastewater treatment plants of petrochemical industries for enhanced biodegradation and contaminant removal. The application of electric field on PS through direct current is optimized with the combined variation of applied voltage (40–80 V), exposure duration (20–120 min) and distance between graphite electrodes (8–16 cm) using central composite design-response surface methodology (CCD-RSM). The optimization study revealed significant interaction among the response variables to obtain an optimum condition (60 V, 83.5 min, 11.6 spacing) for maximization of solubilization in terms of soluble chemical oxygen demand (230% increment against untreated) and volatile fatty acids (172% increment against untreated) concentrations for accelerated hydrolysis of complex PS. BMP batch assays were performed at different inoculum and sludge ratios (0.3, 0.4, 0.5 and 0.7) based on volatile solids content after pretreatment at the optimized condition which resulted in accumulated methane ranging from 5.16 to 6.61 L/gVSadded (untreated - 3.9 L/gVSadded). The mixing ratio of 0.4 showed the maximum methane enhancement of 69.2% compared to untreated. The maximum removal of organic content (62.8%), oil and grease (71.74%), and total petroleum hydrocarbon (52.9%) were also observed for the mixing ratio of 0.4. The FTIR study showed the efficacy in hydrocarbon dissociation and decomposition after pretreatment of PS. The net energy gain (3508 kJ) and phytotoxicity reduction of batch digestate after the anaerobic digestion suggest the economic feasibility and decontamination efficiency of the electrokinetic pretreatment technique respectively. Further research could be performed to evaluate the viability of this pretreatment for enhanced methane recovery at field-scale levels to relate to these lab-scale postulations.

Recent Approaches for the Production of High Value-Added Biofuels from Gelatinous Wastewater

Gelatin production is the most industry polluting process where huge amounts of raw organic materials and chemicals (HCl, NaOH, Ca2+) are utilized in the manufacturing accompanied by voluminous quantities of end-pipe effluent. The gelatinous wastewater (GWW) contains a large fraction of protein and lipids with biodegradability (BOD/COD ratio) exceeding 0.6. Thus, it represents a promising low-cost substrate for the generation of biofuels, i.e., H2 and CH4, by the anaerobic digestion process. This review comprehensively describes the anaerobic technologies employed for simultaneous treatment and energy recovery from GWW. The emphasis was afforded on factors affecting the biofuels productivity from anaerobic digestion of GWW, i.e., protein concentration, organic loading rate (OLR), hydraulic retention time (HRT), the substrate to inoculum (S0/X0) ratio, type of mixed culture anaerobes, carbohydrates concentration, volatile fatty acids (VFAs), ammonia and alkalinity/VFA ratio, and reactor configurations. Economic values and future perspectives that require more attention are also outlined to facilitate further advancement and achieve practicality in this domain.

Effect of poultry litter biochar on the biomethanation of alkaline wet air-oxidized water hyacinth at high feed to inoculum (F/I) ratio

Effect of poultry litter biochar on the biomethanation of alkaline wet air-oxidized water hyacinth at high feed to inoculum (F/I) ratio