Domestic wastewater as substrate for cellulase production by Trichoderma harzianum

Cellulase and chitinase activities and antagonism against Fusarium oxysporum f.sp. cubense race 1 of six Trichoderma strains isolated from Mexican maize cropping

OBJECTIVE

To evaluate the enzymatic and biocontrol capacity of native Trichoderma strains isolated from corn crops in Irapuato (state of Guanajuato) and Napízaro (state of Michoacán), Mexico.

RESULTS

Six native strains from Irapuato and Napízaro were tested, with five of them identified as T. harzianum and one as T. tomentosum. The six strains qualitatively and quantitatively showed enzyme activity for cellulase and chitinase. The best results were obtained for strains IrV6SIC7 and MichV6S2C2 with 878 IU L^-1 of chitinase and 1323 IU L^-1 of cellulase, respectively. All Trichoderma strains acted antagonistically toward Fusarium oxysporum f.sp. cubense race 1 (FocR1), with percentages of inhibition that ranged from 9 to 54%. In addition, the microscopic analysis allowed visualizing the mechanisms of mycoparasitism and antibiosis by either IrV6SIC7 or MichV6S2C2. The latter effects indicate that the tested native Trichoderma strains isolated from corn crops possessed enzymatic mechanisms as a strategy for biocontrolling FocR1 strains.

CONCLUSION

The enzyme production by the Trichoderma strains represents a potential biotechnological utilization for either agricultural or industrial purposes.

A non-waste strategy for enzymatic hydrolysis of cellulose recovered from domestic wastewater

Cellulose is a potential resource to be recovered from wastewater treatment plants (WWTP). Enzyme formulations can be employed to hydrolyze cellulose into fermentable sugars, to be further used as biochemical building blocks or reducing its recalcitrance to further treatment processes. This study proposed the production, recovery and formulation of cellulase using domestic wastewater as culture medium and its application for the hydrolysis of cellulosic residues recovered from WWTPs. Cellulose was recovered from raw sanitary wastewater using a fine-mesh sieve (0.35 mm) and quantified through enzymatic hydrolysis and thermogravimetric analysis. The production, concentration and formulation of cellulase enzyme resulted in an enzymatic blend of endoglucanases (7.3 U_FP/mL), cellobiohydrolases (7.4 U_CMC/mL) and beta-glucosidases (4.4 U_BGL/mL). The content of the recovered cellulosic material was 21.3% according to enzymatic hydrolysis and 27.7 for thermogravimetric results. The enzymatic hydrolysis of the WWTP residue using the produced cellulase (107.6 ± 10.2 mg_reduc/g_residue) showed better results than using the commercial cellulase complex (66.4 ± 2.5 mg_reduc/g_residue). This fact showed the potential of application of the produced enzyme for the hydrolysis of cellulosic residues recovered from WWTP processes. In a non-waste biorefinery approach, the generated hydrolysate can be further used for producing added-value biomolecules including biofuels and biochemicals.

Bioenergy from dairy manure: technologies, challenges and opportunities

Dairy manure (DM) is a kind of cheap cellulosic biomass resource which includes lignocellulose and mineral nutrients. Random stacks not only leads damage to the environment, but also results in waste of natural resources. The traditional ways to use DM include returning it to the soil or acting as a fertilizer, which could reduce environmental pollution to some extent. However, the resource utilization rate is not high and socio-economic performance is not utilized. To expand the application of DM, more and more attention has been paid to explore its potential as bioenergy or bio-chemicals production. This article presented a comprehensive review of different types of bioenergy production from DM and provided a general overview for bioenergy production. Importantly, this paper discussed potentials of DM as candidate feedstocks not only for biogas, bioethanol, biohydrogen, microbial fuel cell, lactic acid, and fumaric acid production by microbial technology, but also for bio-oil and biochar production through apyrolysis process. Additionally, the use of manure for replacing freshwater or nutrients for algae cultivation and cellulase production were also discussed. Overall, DM could be a novel suitable material for future biorefinery. Importantly, considerable efforts and further extensive research on overcoming technical bottlenecks like pretreatment, the effective release of fermentable sugars, the absence of robust organisms for fermentation, energy balance, and life cycle assessment should be needed to develop a comprehensive biorefinery model.

Current perspective on production and applications of microbial cellulases: a review

The potential of cellulolytic enzymes has been widely studied and explored for bioconversion processes and plays a key role in various industrial applications. Cellulase, a key enzyme for cellulose-rich waste feedstock-based biorefinery, has increasing demand in various industries, e.g., paper and pulp, juice clarification, etc. Also, there has been constant progress in developing new strategies to enhance its production, such as the application of waste feedstock as the substrate for the production of individual or enzyme cocktails, process parameters control, and genetic manipulations for enzyme production with enhanced yield, efficiency, and specificity. Further, an insight into immobilization techniques has also been presented for improved reusability of cellulase, a critical factor that controls the cost of the enzyme at an industrial scale. In addition, the review also gives an insight into the status of the significant application of cellulase in the industrial sector, with its techno-economic analysis for future applications. The present review gives a complete overview of current perspectives on the production of microbial cellulases as a promising tool to develop a sustainable and greener concept for industrial applications.

Improving β-glucosidase and xylanase production in a combination of waste substrate from domestic wastewater treatment system and agriculture residues

Cellulase and hemicellulase activities are considered to the major bottlenecks in the lignocellulosic biorefinery process, especially in an enzyme cocktail lacking β-glucosidase (BGL) and xylanase (XYL). In view of this issue, higher levels of BGL and XYL activities were obtained in the presence of wastewater and activated sludge as an induction medium mixed with 5% of rice straw by Hypocrea sp. W₆₃. The analysis of the ionic content showed that a relatively low sludge dose could enhance the production of BGL and XYL. Most importantly, compared to a medium using freshwater, the proportion of 1:10 sludge to wastewater, which contained nutrient elements, led to 3.4-fold BGL and 3.7-fold XYL production improvements. This research describes the reuse of substrates that are largely and continuously generated from domestic wastewater treatment systems and agriculture residues, which consequently leads to the development of a simultaneous enzyme production process for sustainable biorefinery practices.

Rhodopseudomonas sphaeroides treating mesosulfuron-methyl waste-water

The soybean processing wastewater (SPW) supplementation to facilitate the simultaneously treatment (SPW and mesosulfuron-methyl) of wastewater and production of biological substances by Rhodopseudomonas sphaeroides (R. sphaeroides) was discussed. Compared with the control group, with the addition of SPW, mesosulfuron-methyl was removed, and the yields of single-cell proteins, carotenoids, and bacteriochlorophyll were increased. In the 3 mg/L dose group, the mesosulfuron-methyl removal rate reached 97% after 5 days. Molecular analysis revealed that mesosulfuron-methyl exhibited induction effects on expression of the cpm gene and regulation effects on the synthesis of cytochrome P450 monooxygenases (P450) by activating HKs gene in TCS signal transduction pathway. For R. sphaeroides, this induction process required 1 day. The synthesis of P450 occurred 1 day after inoculation. Prior to expressing cpm gene and synthesizing P450, R. sphaeroides need a period of time to adapt to external mesosulfuron-methyl stimulation. However, the R. sphaeroides growth could not be maintained for more than 1 day due to the lack of organic matter in the raw wastewater. The SPW supplementation provided a sufficient carbon source in four groups with added SPW. After 5 days, R. sphaeroides became the dominant microflora in the wastewater. This new method could complete the treatment of mixed wastewater, the increased of biological substances output and the reuse of wastewater and R. sphaeroides cells as resources at the same time.

Biodegradation of fluoroquinolone antibiotics and the climbazole fungicide by Trichoderma species

Filamentous fungi Trichoderma have been able to efficiently degrade fluoroquinolone antibiotics namely ciprofloxacin (CIP) and ofloxacin (OFL) as well as the fungicide climbazole (CLB) that are persistent in conventional activated sludge processes. All targeted compounds were biotransformed by whole cells of Trichoderma spp., exactly T. harzanium and T. asperellum, and biosorption played a limited role in their elimination. However, contrasting results were obtained with the two strains. T. asperellum was more efficient against CIP, with a 81% degradation rate in 13 days of incubation, while T. harzianum was more efficient against CLB, with a 91% degradation rate. While in the case of OFL, both strains showed same efficiency with degradation rate around 40%. Adding a cytochrome P450 enzyme inhibitor hardly resulted in the modification of degradation kinetics supporting the implication of extracellular enzymes in chemical biotransformation. Transformation products were identified by liquid chromatography-high resolution-mass spectrometry and transformation pathways were proposed. Biotransformation of selected compounds included hydroxylation, oxidation/reduction and N- and O-dealkylation reactions, similarly to those reported with white rot fungi. CIP underwent transformations at the piperazinyl ring through oxidation and conjugation reactions, while OFL mainly underwent hydroxylation processes and CLB carbonyl reduction into alcohol. Consequently, Trichoderma spp. likely possess a machinery of unspecific enzymes, which makes their application in removal of pharmaceutical and personal care products attractive.

RETRACTED: Clothianidin wastewater treatment and the accumulation of high-value biochemical by Rhodopseudomonas spheroides

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Authors and the Editor-in-Chief. The paper is retracted because of a high level of duplication of "Rhodopseudomonas palustris wastewater treatment: cyhalofop-butyl removal, biochemicals production and mathematical model establishment. Bioresource. Tech. 2019, 282: 390-397 As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process. The first author, Pan Wu, takes full responsibility for these actions, a stance supported by Dalian Minzu University and Northeast Agricultural University, Harbin, where the research took place.

Soybean processing wastewater supported the removal of propyzamide and biochemical accumulation from wastewater by Rhodopseudomonas capsulata

Simultaneous (SPW and propyzamide) wastewater treatment and the production of biochemicals by Rhodopseudomonas capsulata (R. capsulata) were investigated with supplement of soybean processing wastewater (SPW). Compared to control group, propyzamide was removed and biochemicals production were enhanced with the supplement of SPW. Propyzamide induced camH gene expression through activating MAPKKKs gene in MAPK signal transduction pathway. The induction of camH gene and CamH occurs after 1 day for R. capsulata. However, lack of organics in original wastewater did not maintain R. capsulata growth for over 1 day. The supplement of SPW provided sufficient carbon source for R. capsulata under three addition dosages. This new method resulted in the mixed (SPW and propyzamide) wastewater treatment and improvement of biochemicals simultaneously, as well as the realization of reutilization of wastewater and R. capsulata as sludge. Meanwhile, high-order nonlinear mathematical model of the relationship between propyzamide removal rate, Xt and Xt/r, was established.

Definition of Liquid and Powder Cellulase Formulations Using Domestic Wastewater in Bubble Column Reactor

Raw domestic wastewater was used as a culture medium for cellulase production in a bubble column reactor (6.2 U_FP/mL, 64.6 U/L h) using the strain Trichoderma harzianum TRIC03-LPBII. Cellulases presented optimum pH and temperature between 4 and 5 and 50 and 70 °C, respectively. Enzymatic extract was concentrated through ultrafiltration and then a cellulolytic formulation was prepared with the addition of sorbitol (50% w/v) and benzoic acid (0.05% w/v). High cellulase stability of around 100% was reached after 30 days at 4 °C. The concentrated extract was also dried in a spray-dryer with the addition of maltodextrin at 20% (w/v), resulting in powder enzymatic formulation with 85% stability after 60 days. With these characteristics, the liquid and powder cellulase products have potential to be used in different industrial applications.

Rhodopseudomonas palustris wastewater treatment: Cyhalofop-butyl removal, biochemicals production and mathematical model establishment

Simultaneous (SPW and cyhalofop-butyl) wastewater treatment and the production of biochemicals by Rhodopseudomonas palustris (R. palustris) was investigated with supplementation of soybean processing wastewater (SPW). Compared to control group, cyhalofop-butyl was removed and single cell protein, carotenoid, bacteriochlorophyll productions were enhanced with the supplementation of SPW. Cyhalofop-butyl removal reached 100% after 5 days under 4000 mg/L COD group. Cyhalofop-butyl induced chbH gene expression to synthesize cyhalofop-butyl-hydrolyzing carboxylesterase through activating MAPKKKs, MAPKKs, MAPKs genes in MAPK signal transduction pathway. The induction process took one day for R. palustris. However, lack of organics in original wastewater did not maintain R. palustris growth for over one day. The supplementation of SPW provided sufficient carbon source. This new method resulted in the mixed wastewater treatment and improvement of biochemicals simultaneously, as well as the realization of reutilization of R. palustris. High-order non-linear mathematical model of the relationship between R_chb, X_c, and X_t was established.

Simultaneous cellulase production using domestic wastewater and bioprocess effluent treatment - A biorefinery approach

The production of cellulases using domestic wastewater as an alternative culture medium and reducing the pollutant charge of the resultant effluents were assessed for the first time in this study. Cellulase production was carried out in a bubble column, column-packed bed and stirred tank reactors by Trichoderma harzianum. Maximum cellulase activity and productivity of 31 U_FP/mL and 645 U_FP/mL.h, respectively were achieved in the bubble column bioreactor system without immobilization. The fermented broth was microfiltrated and ultrafiltrated, leading to a cellulase recovery of 73.5% using a 30 kDa membrane and resulting in a 4.23-fold activity concentration. Chemical oxygen demand and nitrogen concentration were reduced 81.37% and 52.9%, respectively, showing great promise in producing cellulases using domestic wastewater with concomitant development of a medium- to-high added-value process and reduced environmental impact. These results contribute to the development of sustainable bioprocesses approaching a biorefinery concept.

Polycyclic aromatic hydrocarbon-emulsifier protein produced by Aspergillus brasiliensis (niger) in an airlift bioreactor following an electrochemical pretreatment

An emulsifier protein (EP) was produced and easily separated from oil-contaminated water as an economical substrate when Aspergillus brasiliensis, pretreated in a solid state culture with a controlled electric field, was used in an airlift bioreactor. The hydrocarbon-EP comprised 19.5% of the total protein, its purification enhanced the specific emulsifying activity (EA) seven times. The influence of operational conditions (pH and salt concentration) on the EA were assessed to characterise the emulsion stability. The EA was increased by 19% in alkaline environments (pH 7-11), but it was not affected by the presence of salt (0-35 g L^-1). On the other hand, preheating the EP samples (60 °C) enhanced the EA by 2.5 times. Based on analysis of its EA, this EP can be applied as a bioremediation enhancer in contaminated soils.

Improving the methane yield of maize straw: Focus on the effects of pretreatment with fungi and their secreted enzymes combined with sodium hydroxide

In order to improve the methane yield, the alkaline and biological pretreatments on anaerobic digestion (AD) were investigated. Three treatments were tested: NaOH, biological (enzyme and fungi), and combined NaOH with biological. The maximum reducing sugar concentrations were obtained using Enzyme T (2.20 mg/mL) on the 6th day. The methane yield of NaOH + Enzyme A was 300.85 mL/g TS, 20.24% higher than the control. Methane yield obtained from Enzyme (T + A) and Enzyme T pretreatments were 277.03 and 273.75 mL/g TS, respectively, which were as effective as 1% NaOH (276.16 mL/g TS) in boosting methane production, and are environmentally friendly and inexpensive biological substitutes. Fungal pretreatment inhibited methane fermentation of maize straw, 15.68% was reduced by T + A compared with the control. The simultaneous reduction of DM, cellulose and hemicellulose achieved high methane yields. This study provides important guidance for the application of enzymes to AD from lignocellulosic agricultural waste.