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The concept of utilizing various types of wastes, such as agricultural dumps and marine by-products, as a partial replacement of cement has gained a great interest to develop eco-friendly and economical mortars for sustainable construction. This study aims to evaluate the feasibility of using palm oil fuel ash (POFA), an agro-industrial waste by-product from palm oil mills and seashell powder (SSP) derived from seashells, a marine waste material partial replacement of cement in mortars. The water to binder (w/b) ratio of 0.49 and the sand to binder (s/b) ratio of 2.54 with 0% to 30% of ordinary portland cement (OPC) by weight was replaced with POFA and SSP, and the resulting mortar samples were tested for mechanical properties and durability in this study. The compressive strength, flexural strength, water absorption, and flow table tests were performed in this study for different percentages of POFA and SSP after 7, 28, and 130 days. The results showed that the 30% POFA incorporated mortars achieved the highest compressive strength (35.12N/mm2), flexural strength (4.06N/mm2), high density with less water absorption (4.79%) after 130 days of curing and the high strength mortar with less water flow (22.2cm) during casting. Also, it found that the 25% POFA and 5% SSP incorporated mortars attained acceptable results as supplementary cementing material. This study suggests that the POFA and SSP incorporated mortars could be used in concrete for sustainable development of construction through the efficient valorization of waste materials.

Co-cultures of different microorganisms are considered promising inocula for treating palm oil mill effluents (POME) and producing value-added bio-products (e.g., biofuels and fatty acid-derived materials). However, the efficiency of yeast-bacteria co-culture for microbial lipid production through bioremediation of wastewater remains a bottleneck. In this study, the performance of a co-culture for lipid accumulation through POME bioremediation was investigated using a yeast (Lipomyces starkeyi) and a bacterium (Bacillus cereus). A maximum biomass of 8.89 ± 0.33 g/L and lipid production of 2.27 ± 0.10 g/L were achieved by the co-culture inoculum, which were substantially higher than those of the monocultures. Besides, the co-culture inoculum attained a maximum chemical oxygen demand (COD) removal of 83.66 ± 1.9%, while the individual cultures of B. cereus and L. starkeyi obtained 74.35 ± 1.7% and 69.01 ± 2.3%, respectively. The bioremediation efficiency was confirmed by the seed germination index (GI) of Vigna radiata (Mung bean). It was observed that the co-culture inoculum had a higher GI compared to the untreated POME and even the monoculture-treated POME. We argue that the symbiotic association of a yeast-bacteria co-culture in POME could be an attractive approach for achieving maximum biomass as well as lipid production and simultaneous bioremediation of POME.

The first hypothetical hydrogen (H2) production from biological means was proposed in the early of nineteenth century. However, the biological H2 production technology did not received much attention until the anticipation of H2 production was practically reported through anaerobic digestion of cellulose using microbes present in the ruminant tract in 1930s. Later on, subsequent development on fermentative H2 production has been reported by researchers employing advanced technologies to the fermentative systems. The present review is envisioned to provide a technological devolvement’s towards fermentative H2 production from the late nineteenth to the present twenty-first century. The major technological aspects associated with H2 production through the fermentative process such as genetic engineering, nanomaterial implementations, immobilization techniques, and reactor configuration developments were highlighted in this review.

Whey permeate (WP) is a co-product of a cheese or casein production process that is regarded as an environmental pollutant because of its high organic load and is creating a major disposal problem for the dairy industry. However, it can be used as a suitable substrate to meet the increasing demand of producing a prebiotic lactulose through the isomerization of lactose present in the WP under adequate alkaline conditions. The goal of this study was to produce lactulose in situ of WP using electro-activation (EA) technology and compare the productivity of EA with conventional chemical isomerization at potassium hydroxide (KOH)-equivalent solution alkalinity in the feed medium. Electro-isomerization was conducted under different current intensities of 300, 600, and 900 mA for 60 min of EA with a 5 min sampling interval using 6, 12, and 18% (w/v) WP solutions. Chemical isomerization was carried out at the KOH-equivalent solution alkalinity to that measured in the EA solution at each 5 min interval using KOH powder as a catalyst. The outcomes of this study revealed that the production of lactulose using the EA approach was current intensity-, WP concentration-, and reaction time-dependent and produced the highest lactulose yield of 36.98% at 50 min of EA-time under 900 mA current intensity using 6% WP as a feed solution, whereas a maximum lactulose yield of 25.47% was achieved by the chemical isomerization at the solution alkalinity corresponding to that of the EA under 900 mA current intensity at 50 min in the 6% WP solution. Furthermore, a greater yield of lactulose was obtained using the EA technique for all reaction conditions compared to the chemical process at the equivalent solution alkalinity. Therefore, the results of this work suggest that the EA can be an emergent sustainable technology for achieving dual objectives of prebiotic lactulose production and concurrent valorization of WP using it as a feed medium.

The demand for production of prebiotics at a commercial scale is rising due to the consumers' growing health awareness. Whey, a coproduct of the dairy industries, is a suitable feed medium to produce a prebiotic lactulose through the isomerization of lactose under alkaline conditions. The aim of the present study was to compare the isomerization of lactose into lactulose in situ of whey by using electroactivation technology with the chemical isomerization method using KOH as catalysis under equivalent solution alkalinity. Electroisomerization of lactose into lactulose was performed by using whey solutions of 7, 14, and 21% (w/v) dry matter under current intensities of 300, 600, and 900 mA, respectively, during 60 min with a sampling interval of 5 min. The conventional chemical method was carried out using KOH powder as catalyst at the alkalinity that corresponded to that measured in the electroactivated whey at each 5 min interval. The results showed that lactulose production was dependent on the whey concentration, current intensity, and EA time. The highest lactulose yield of 32% was achieved under a 900 mA current intensity at 60 min for a 7% whey solution. Thereafter, the EA conditions were compared to those of a conventional chemical isomerization process by maintaining similar alkalinity in the feed solutions. However, no lactulose was produced by the chemical process for the equivalent solution alkalinity as in the EA technique. These results were correlated with the solution pH, which reached the required values in a 7% whey solution with values of up to pH 11.50, whereas the maximum pH values that were obtained at higher whey concentrations were around 10-10.50, which was not enough to initiate the lactose isomerization reaction. The outcomes of this study suggest that EA is an efficient technology to produce lactulose using whey lactose.

The demand of lactulose production is increasing tremendously because of its bifidogenic (prebiotic) functionality. Therefore, the isomerization of lactose to synthesize lactulose through electroactivation (EA) technology is of great interest nowadays. However, lactulose production through electroisomerization is affected by several operational and experimental conditions, and the process needs to be optimized. In this context, the EA technique was applied to isomerize lactose into lactulose in an EA reactor modulated by anion and cation exchange membranes. The effect of lactose concentrations (5, 10, 15, and 20%), applied electric fields (300, 600, and 900 mA), and processing time (0-60 min) on lactose electroisomerization rate (lactulose formation) and coproduct (glucose, galactose, and fructose) formation has been investigated. The effect of different physicochemical parameters such as pH, alkalinity, temperature, ion migration, and oxidation-reduction potential (ORP) on the conversion of lactose into lactulose was correlated with the lactulose formation to understand the involved process mechanism of action. The conversion of lactose into lactulose was lactose-concentration-, electric-current-, and EA-time-dependent and reached the highest lactulose yield of 38% at 40 min using a 900 mA current intensity in a 10% lactose solution. The results were then compared to conventional chemical isomerization maintaining similar alkaline conditions at ambient temperature (22 ± 2 °C). A higher yield of lactulose was achieved in the EA process within a short reaction time compared to that of the chemical isomerization. The outcome of this study suggests that EA is a promising technique for the enhanced production of lactulose from lactose.

The wastewater burden and increased energy demands have spurred interest in finding possible solutions that could concomitantly address both issues. Microbial lipid production, together with the bioremediation of wastewater, could be a promising solution to address both problems. In this context, the present study was designed to evaluate the potential of Bacillus cereus (B. cereus) for accumulating microbial lipids through the bioremediation of palm oil mill effluent (POME) in batch mode fermentation. Different dilutions of POME media (25%, 50%, 75%, and 100%) were used to determine the optimum POME concentration for enabling the maximum yield of biomass and maximum lipid production. The 50% (v/v) POME was found to have potential for the highest biomass growth (8.09 g/L) and lipid accumulation (1.46 g/L), with a lipid content of 18.04% (dry weight basis). B. cereus accumulated a higher biomass and lipid content than other bacterial strains, such as Rhodococcus opacus and Pseudomonas aeruginosa, under similar conditions. On the other hand, the degree of bioremediation was assessed by evaluating several wastewater parameters and determining the seed germination index (GI) of Vigna radiata. POME treated with B. cereus displayed higher GI values than the untreated samples due to the significant remediation of detrimental organics present in the POME. This finding was further confirmed by the substantial reduction in pollution load, particularly in chemical oxygen demand (COD) and biochemical oxygen demand (BOD) for 50% POME, thus demonstrating removal efficiencies of 79.35% and 72.65%, respectively. Therefore, the results of this study suggest that B. cereus cultivation in POME could be a promising technique for attaining higher biomass growth and lipid production in conjunction with the bioremediation of POME. The approach of achieving dual objectives that is utilized in the present study provides a novel strategy for palm oil millers.

Whey and whey permeate (WP) are the main by-products from cheese or casein manufacturing process and there is a serious demand of developing a sustainable approach for their utilization to evade environmental pollution. The objective of this study was to explore the feasibility of using electro-activated (EA) whey-based substrates (whey, WP, lactose) as carbon sources to produce valuable metabolites including organic acids (i.e., lactic, acetic, citric, and propionic acids), exopolysaccharides (kefiran), and volatile flavour compounds using the whole kefir grains as a starter culture. Fermentation was performed by inoculating a mixed microbiota from kefir grains in EA and non-EA solutions of lactose, whey, and WP and were statically incubated for 96 h at 30 ℃. The results showed that the EA substrates achieved a higher biomass growth in a reduced fermentation time than their non-EA mediums. The highest cell growth (6.04 g/L) was obtained for EA-whey after 72 h which was even 1.7-fold higher than a standard nutrition broth, the reinforced clostridial medium (RCM). Furthermore, EA-whey produced a maximum of 8.46, 3.97, 0.60, and 1.02 g/L of lactic, acetic, citric, and propionic acid, respectively. Moreover, EA-whey achieved the highest kefiran production of 2.99 g/L, followed by the whey (2.67 g/L), EA-WP (2.31 g/L), WP (1.88 g/L), RCM broth (1.42 g/L), EA-lactose (1.37 g/L), and lactose (0.91 g/L). The results also demonstrated that various aromatic volatile compounds were produced during the fermentation of EA-whey, which may increase the organoleptic characteristic/sensory quality of the fermented products. Thus, the results of the present study provide a strong evidence that the EA-substrates, especially EA-whey, could be potential feedstock to develop an efficient bioprocess for producing valuable metabolites using kefir grains as a suitable starter.

Blood serum metabolites of enzymes, lipids and proteins were chosen to compare between two groups of fresh water fish as control group and trained group. As a result of regular programmed workout regime some alterations in metabolites content were recorded. Comparative analysis of metabolite contents revealed minor fall downin HDL cholesterol whereas hepatic and bile activities were found normal as AST and ALT did not show reductive tendency. Ion metabolites did not show any major alteration except Na that may be due to age related changes during the training routine. On the basis of comparison, it may be concluded that regular but non-intense exercise will cause moderate changes in the basal metabolism of fresh water fishes. &nbsp

The present study embarked on investigating the photo-fermentative bio-H2 production kinetics and statistical optimization of operational parameters using immobilized inoculum from dark fermented palm oil mill effluent (DPOME). The statistical optimized values of initial pH, inoculum-substrate percentage (ISP), and light intensity were achieved by implicating the central composite design (CCD) under response surface methodology (RSM). The kinetic evaluation was conducted in terms of H2-yield with ISP ranged from 10 to 30%. The highest H2 production potential (P) and rate (Rmax) of 30.59 ml.H2/g-CODremoved and 0.514 ml h−1 respectively were achieved with reported lag phase (ρ) value of 32 h by using 20% of ISP. However, an observed Rmax of 0.746 with a ρ value of 39 h was attained at ISP of 15%. The quadratic model developed by using CCD was observed to display the significance value of < 00.5 of probability error. Additionally, observed values of correlation coefficient (R2), adequate precision (AP), and coefficient of variance (CV) for acquired H2-yield were 0.9219, 12.076, and 11.24 ml.H2/g-CODremoved, respectively. Under optimal conditions values (initial pH, 6.0; ISP, 20%; and light intensity, 350% W/m2), H2 yield of 147 ml.H2/g-CODremoved was achieved from DPOME, while reducing the COD value by 78 percentage. This statistical model is suggested to possess the regression, interaction, and quadratic terms as significant, so it can be deemed acceptable in terms of its achievable reproducibility.

Several yeasts, which are eukaryotic microorganisms, have long been used in different industries due to their potential applications, both for fermentation and for the production of specific metabolites. Kluyveromyces marxianus is one of the most auspicious nonconventional yeasts, generally isolated from wide-ranging natural habitats such as fermented traditional dairy products, kefir grain, sewage from sugar industries, sisal leaves, and plants. This is a food-grade yeast with various beneficial traits, such as rapid growth rate and thermotolerance that make it appealing for different industrial food and biotechnological applications. K. marxianus is a respiro-fermentative yeast likely to produce energy by either respiration or fermentation pathways. It generates a wide-ranging specific metabolites and could contribute to a variety of different food and biotechnological industries. Although Saccharomyces cerevisiae is the most widely used dominant representative in all aspects, many applications of K. marxianus in biotechnology, food and environment have only started to emerge nowadays; some of the most promising applications are reviewed here. The general physiology of K. marxianus is outlined, and then the different applications are discussed: first, the applications of K. marxianus in biotechnology, and then the recent advances and possible applications in food, feed and environmental industries. Finally, this review provides a discussion of the main challenges and some perspectives for targeted applications of K. marxianus in the modern food technology and applied biotechnology in order to exploit the full potential of this yeast which can be used as a cell factory with great efficiency.

An understanding of the inter-species relationships, especially their metabolic network in a mixed-culture system, is crucial to design an effective inoculum for enhancing the power generation of wastewater fed microbial fuel cell (MFC). In the present study, the influence of microbial mutualistic interactions on the power generation of palm oil mill effluent fed MFCs has been widely investigated by designing several co-culture and mixed culture inoculums. Among the different inoculum compositions, the highest power density of 14.8 W/m3 was achieved by Pseudomonas aeruginosa and Klebsiella variicola co-culture inoculum due to their synergistic relationships which were inter-linked via fermentation-based metabolites. Besides, the interaction of K. variicola and Bacillus cereus positively influenced the power generation resulting in a maximum power density of 11.8 W/m3 whereas the antagonistic relationship between B. cereus and P. aeruginosa resulted in a lower power generation of 1.9 W/m3. The microbial mutualistic interactions were investigated with polarization, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), as well as by using metabolite and biofilm analysis. It was observed that the synergism between bacteria enhanced power generation through the production of higher electron shuttling mediators and efficient biofilm formation as evidenced by polarization, CV and EIS analysis. In contrast, the antagonistic relationship resulted in production of cell inhibiting metabolites leading to the formation of ineffective biofilm. These findings demonstrate that the synergistic interaction between or within microorganisms is emergent in designing co-culture or mixed-culture inoculum for achieving maximum power generation in MFCs.

Microalgal biofuels are considered as one of the most promising substitutes to the nonrenewable fossil fuels. However, the efficient recovery of microalgal lipids is emergent for the overall process economics and sustainability. The conventional lipid extraction technique entails direct use of organic solvents to liberate the intracellular lipids, thus making the extraction process more time-consuming and less eco-friendly. Furthermore, the efficiency of extraction process is affected by several problems, such as the rigid structure and composition of microalgal cell walls, the water content of biomass, the limited accessibility of lipids, the reduced mass transfer, and the formation of stable emulsions. Various modifications (e.g., use of green solvents, direct transesterification, pretreatment for disrupting microalgal cells, etc.) to conventional lipid extraction have been proposed to mitigate the problems associated with lipid extraction. Among them, the pretreatment approach (i.e., mechanical, chemical, biological cell disruption) in combination with solvent-based extraction would be a promising approach to address the problems during lipid extraction. Therefore, intensive research, review, and analysis are required to understand the challenges in lipid extraction and to develop a useful extraction process in terms of biomass status (dry/wet), solvent use, lipid yield, extraction time, and scalability. In this chapter, we have reviewed the composition and possible applications of microalgal lipids with the main challenges in their extraction process. Furthermore, the advantages and limitations of several pretreatment methods for cell disruption have been comprehensively discussed.

The depletion of nonrenewable energy sources drives the exploration for renewable energy sources as an alternation route of energy generation. Hence, in the past decade, research efforts have been employed to explore potential renewable energy sources utilizing waste biomass. Anaerobic digestion (AD) is considered as an efficient technique to treat different kinds of wastes such as agricultural, industrial, and food wastes to produce renewable energy. Until now, two predominant fermentation processes, namely submerge or liquid-state anaerobic fermentation (LSAF) and dry or solid-state anaerobic fermentation (SSAF) have been implemented to extract energy from waste biomass. Nowadays, SSAF is claimed to be more advantageous than LSAF for a number of reasons including its comparatively smaller reactor volume, lower energy requirements for heating, minimal material handling, and lower total parasitic energy loss. Due to its low moisture content, the digestate of SSAF can be used as fertilizer or pelletized fuel, which is much easier to handle than the effluent from LSAF. However, for enhancing the performance of dry AD processes, a suitable reactor needs to be designed so that the maximum amount of substrate could be fermented, to make the technology more economically viable. Therefore this chapter is aimed at discussing the different kinds of bioreactors along with their potential benefits, challenges, and limitations, which have been explored recently for biogas production through dry fermentation.

The detection of pathogenic bacteria using biosensing techniques could be a potential alternative to traditional culture based methods. However, the low specificity and sensitivity of conventional biosensors, critically related to the choice of bio-recognition elements, limit their practical applicability. Mammalian antibodies have been widely investigated as biorecognition ligands due to high specificity and technological advancement in antibody production. However, antibody-based biosensors are not considered as an efficient approach due to the batch-to-batch inconsistencies as well as low stability. In recent years, antimicrobial peptides (AMPs) have been increasingly investigated as ligands as they have demonstrated high stability and possessed multiple sites for capturing bacteria. The conjugation of chemo-selective groups with AMPs has allowed effective immobilization of peptides on biosensor surface. However, the specificity of AMPs is a major concern for consideration as an efficient ligand. In this article, we have reviewed the advances and concerns, particularly the selectivity of AMPs for specific detection of pathogenic bacteria. This review also focuses the state-of-the-art mechanisms, challenges and prospects for designing potential AMP conjugated biosensors. The application of AMP in different biosensing transducers such as electrochemical, optical and piezoelectric varieties has been widely discussed. We argue that this review would provide insights to design and construct AMP conjugated biosensors for the pathogenic bacteria detection.

Electro-activated whey (EA-whey), electro-activated whey permeate (EA-WP) and electro-activated lactose (EA-lactose) were explored as carbon sources to produce valuable metabolites including organic acids, exopolysaccharides, and volatile flavour compounds using kefir grains as a starter culture. The results showed that the EA-substrates achieved a higher biomass growth in a reduced fermentation time than their non-EA counterparts. The highest cell growth (6.04 g L-1) was obtained for EA-whey, which was even 1.7-fold higher than a standard nutrition broth. Furthermore, EA-whey produced a maximum of 8.46, 3.97, 0.60, and 1.02 g L-1 of lactic, acetic, citric, and propionic acid, respectively. Likewise, EA-whey achieved the highest kefiran production of 2.99 g L-1. Nevertheless, production of numerous aromatic volatile compounds during fermentation of EA-whey may improve organoleptic characteristic of the fermented products. Thus, the EA-substrates, especially EA-whey, could be potential feedstock to develop bioprocesses for producing valuable metabolites using kefir grains as a suitable starter.

Whey is usually considered as an environmental pollutant due to its elevated organic load. Whey production is gradually increasing because of the high demand of milk-derived products. It creates a huge disposal problem for dairy industries. Several efforts have been made to transform whey into added value products. The conversion of lactose into prebiotic lactulose is advantageous because the demand of lactulose is increasing. With an intention to gain deeper insights into lactulose synthesis through sustainable valorisation of whey, this review compiles commonly practiced isomerisation techniques along with their limitations. A descriptive and comprehensive survey is presented to explain the characteristics of whey and its potential for producing different bioproducts. The efficacy of electro-activation as a potential nonconventional technology to produce lactulose through effective utilisation of whey and their process mechanisms are reviewed. This review argues to deliver a broader understanding for effective lactulose production through integral valorisation of whey.

In the present study, the applicability of electroporation (EP) has been investigated as a pretreatment method for enriching hydrogen producers and eliminating hydrogen consumers in anaerobic sludge (AS). Citrus wastewater was used as a feed source for biohydrogen production. Different treatment intensities (TI) of EP for 0.5 min (TI = 30 kWh/m3), 1 min (TI = 60 kWh/m3), and 2 min (TI = 120 kWh/m3) were employed to observe the effects of EP on the microbial community of AS. Furthermore, sonication with a probe, sonication in a bath, and heat-shock pretreatments were also conducted to compare the hydrogen yield with EP. The cell inactivation was evaluated and visualized using colony-forming units (CFU) and field emission scanning electron microscopy (FESEM), respectively. Among the different TIs, the TI of 60 kWh/m3 achieved higher methanogen inactivation with maximum hydrogen (896 mL) production compared to other EP pretreatments after 180 h of dark fermentation. In comparison with other pretreatments, the highest hydrogen production of 896 mL was achieved with EP treatment, followed by sonication with a probe (678 mL) and sonication in a bath (563 mL). The heat-shock pretreatment exhibited the lowest ultimate hydrogen production of 545 mL among the four different methods applied in this study. The outcome of this study suggests that EP is a promising technique for pretreating mixed cultures for the enhanced production of biohydrogen.

The aim of the study was to investigate the feasibility of using irreversible electroporation (EP) as a microbial cell disruption technique to extract intracellular lipid within short time and in an eco-friendly manner. An EP circuit was designed and fabricated to obtain 4 kV with frequency of 100 Hz of square waves. The yeast cells of Lipomyces starkeyi (L. starkeyi) were treated by EP for 2-10 min where the distance between electrodes was maintained at 2, 4, and 6 cm. Colony forming units (CFU) were counted to observe the cell viability under the high voltage electric field. The forces of the pulsing electric field caused significant damage to the cell wall of L. starkeyi and the disruption of microbial cells was visualized by field emission scanning electron microscopic (FESEM) image. After breaking the cell wall, lipid was extracted and measured to assess the efficiency of EP over other techniques. The extent of cell inactivation was up to 95% when the electrodes were placed at the distance of 2 cm, which provided high treatment intensity (36.7 kWh m-3 ). At this condition, maximum lipid (63 mg g-1 ) was extracted when the biomass was treated for 10 min. During the comparison, EP could extract 31.88% lipid while the amount was 11.89% for ultrasonic and 16.8% for Fenton's reagent. The results recommend that the EP is a promising technique for lowering the time and solvent usage for lipid extraction from microbial biomass. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:838-845, 2018.

The discharge of palm oil mill effluent (POME) on arable land causes large amounts of environmental distress due to its high concentration of phenolic compounds and chemical oxygen demand (COD). The approach of simultaneous microbial oil production and wastewater treatment is an attractive option to combine renewable energy production and environmental resilience. This study aims to produce cost effective microbial lipids using the oleaginous yeast Lipomyces starkeyi through the bioremediation of POME. A moderately dilute solution (50%) of POME showed higher microbial growth and lipid accumulation and offered a significantly higher degree of bioremediation. A lipid content of 21.32% was achieved with 50% POME, whereas the value was 15.14% for 25% POME. Three different techniques including ultrasonic treatment, Fenton's reagent and Fenton's + ultrasonic were employed to extract lipids from microbial biomass, and the maximum lipid concentration was obtained using the Fenton's + ultrasonic treatment. The degree of bioremediation was evaluated by the calculating seed germination index (GI) values. Higher GI values were observed for the 25% and 50% dilutions compared to undiluted (100%) POME. This combined approach can be a potential alternative technology that integrates bioremediation of POME with microbial lipid production.

Biohydrogen production from different types of waste biomass using mixed culture inoculum has been an active research area in recent years. Several emerging techniques has been studied targeting to achieve higher efficiency and competitive hydrogen production through the dark fermentation. However, the production of biohydrogen from complex waste biomass meets the setback of lower final product yield due to the low substrate degradation rate. Besides, hydrogen consuming microbes in the mixed culture impede the rate of biohydrogen production. Thus, the waste biomass substrate and microbial inoculum are highly required to pretreat for enhancing system performance. With the aim to gain deeper insight into waste biomass and inoculum pretreatment techniques, this review compiles recently practiced pretreatment techniques with their limitations. The major challenges of these methods and few strategies to overcome these limitations with future directions are discussed in this review. Moreover, the efficiency of a potential nonconventional pretreatment technique such as electroporation (EP) over traditional techniques to degrade the complex waste biomass and reduce the load of hydrogen consuming microbes in the mixed culture consortium was reviewed. This review argued to provide a deeper insight to develop an efficient pretreatment technique by combining traditional techniques and EP for enhancing mixed culture driven biomass-based hydrogen production.

In the present work, simultaneous power generation and wastewater treatment in the single chamber air cathode microbial fuel cell (MFC) have been enhanced by introducing wild-type Klebsiella variicola (K. variicola) as an efficient inoculum for the anode operated with palm oil mill effluent (POME). K. variicola was isolated from municipal wastewater (MWW) and identified using BIOLOG gene III analysis, PCR and sequencing. The performance of K. variicola in MFC was evaluated by polarization curve measurement, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) analysis. The MFC with K. variicola achieved a maximum power density of about 1.7 W m−3 which is comparatively higher than most widely used anaerobic sludge (215 mW m−3) as an inoculum whereas COD removal efficiency is (43%) lower than anaerobic sludge (74%). Moreover, K. variicola has the ability to produce electron shuttles and to form biofilms on the electrode surface which helps to significantly reduce the anode charge transfer (Rct) resistance compared to the anaerobic sludge. These results revealed the potential of K. variicola to be used in MFC.

Biogas is a type of renewable energy which provides clean energy, reduces environmental pollution and greenhouse gas caused by the biological wastes, creates job opportunity for skilled and unskill...