Protein-rich Waste Research Articles

A Review of the Latest Advances in Encrypted Bioactive Peptides from Protein-Rich Waste.

Bioactive peptides are considered the new generation of biologically active regulators that not only prevent the mechanism of oxidation and microbial degradation in foods but also enhanced the treatment of various diseases and disorders, thus increasing quality of life. This review article emphasizes recent advances in bioactive peptide technology, such as: (i) new strategies for transforming bioactive peptides from residual waste into added-value products; (ii) nanotechnology for the encapsulation, protection and release of controlled peptides; and (iii) use of techniques of large-scale recovery and purification of peptides aiming at future applications to pharmaceutical and food industries.

Sustainable synthesis of N and P co-doped porous amorphous carbon using oil seed processing wastes

A facile approach for the sustainable synthesis of amorphous carbons co-doped with N and P (NC) was demonstrated using inexpensive protein rich wastes and H3PO4 as precursors. The prepared NC materials exhibited high degree of aromatization, porosity (specific surface area 435–915m2/g, pore volume 0.34–0.66cm3/g) and nitrogen doping levels of 3.4–9.8at%, depending on intrinsic properties of precursor and synthesis conditions. The materials exhibited electro-catalytic activity for oxygen reduction reaction (ORR) in alkaline electrolytes.

Physiological Effects of GLT1 Modulation in Saccharomyces cerevisiae Strains Growing on Different Nitrogen Sources.

Saccharomyces cerevisiae is one of the most employed cell factories for the production of bioproducts. Although monomeric hexose sugars constitute the preferential carbon source, this yeast can grow on a wide variety of nitrogen sources that are catabolized through central nitrogen metabolism (CNM). To evaluate the effects of internal perturbations on nitrogen utilization, we characterized strains deleted or overexpressed in GLT1, encoding for one of the key enzymes of the CNM node, the glutamate synthase. These strains, together with the parental strain as control, have been cultivated in minimal medium formulated with ammonium sulfate, glutamate, or glutamine as nitrogen source. Growth kinetics, together with the determination of protein content, viability, and reactive oxygen species (ROS) accumulation at the single cell level, revealed that GLT1 modulations do not significantly influence the cellular physiology, whereas the nitrogen source does. As important exceptions, GLT1 deletion negatively affected the scavenging activity of glutamate against ROS accumulation, when cells were treated with H2O2, whereas Glt1p overproduction led to lower viability in glutamine medium. Overall, this confirms the robustness of the CNM node against internal perturbations, but, at the same time, highlights its plasticity in respect to the environment. Considering that side-stream protein-rich waste materials are emerging as substrates to be used in an integrated biorefinery, these results underline the importance of preliminarily evaluating the best nitrogen source not only for media formulation, but also for the overall economics of the process.

Valorisation of protein waste: An enzymatic approach to make commodity chemicals

Protein-rich waste is an abundantly available resource that is currently used mainly as animal feed and fertilizers. Valorisation of protein waste to higher value products, particularly commodity chemicals such as precursors for polymers, has attracted significant research efforts. Enzyme-based approaches, being environmentallyfriendly compared to their chemical counterparts, promise sustainable processes for conversion of protein waste to valuable chemicals. This review provides a general overview on valorisation of protein waste and then further summarises the use of enzymes in different stages of the valorisation process—protein extraction and hydrolysis, separation of individual amino acids and their ultimate conversion into chemicals. Case studies of enzymatic conversion are presented for different amino acids including glutamic acid, lysine, phenylalanine, tyrosine, arginine and aspartic acid. The review compares the different enzyme reactors and operation modes for amino acid conversion. The emerging opportunities and challenges in the field are discussed: engineering powerful enzymes and integrating innovative processes for industrial application at a low cost. Open image in new window

Valorization of tomato waste proteins through production of antioxidant and antibacterial hydrolysates by proteolytic Bacillus subtilis: optimization of fermentation conditions.

In this study, protein-rich waste of tomato processing industries was fermented by Bacillus subtilis A14h to produce hydrolysates with antioxidant and antibacterial activities. The effects of different levels of initial pH, incubation temperature, fermentation time, protein concentration and inoculum size on proteolytic activity, release of amino acids and peptides, antioxidant and antibacterial activities of hydrolysates were evaluated and optimized by using response surface methodology (RSM). Results showed that all the evaluated variables significantly influenced the hydrolysis and bioactivities of hydrolysates in polynomial models. Hydrolysates showed remarkable 2, 2'-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity (up to 70%), ferric ion reducing power, and inhibitory activity against B. cereus (up to 69.8%) and E. coli (up to 29.8%). Overall, good correlation between the concentration of amino acids and peptides, and antioxidant as well as antibacterial activities (in particular for B. cereus inhibition activity) was observed. Finally, optimum conditions for fermentative conversion of tomato waste proteins to antioxidant and antibacterial hydrolysates were established. Results of this study showed that tomato waste protein can be valorized to produce antioxidant and antibacterial hydrolysates in a fermentative system using B. subtilis A14h.

Enhancement of soil suppressiveness against Rhizoctonia solani in sugar beet by organic amendments

The efficacy of different organic soil amendments on disease suppression to Rhizoctoniasolani AG 2-2IIIB was tested in a bio-assay with sugar beet as a test plant. Lysobacter populations in soil were quantified as a possible mechanism for disease suppression. Disease spread through the bio-assay tank was significantly reduced up to 86, 83, 52, and 48% after amending the non-sterilized soil with yeast or chitin at a rate of 0.3% (w/w) in consecutive experiments. Inexpensive protein-rich waste products from food industry (i.e., feather, hoof, meat, blood and fish meal) also effectively increased Rhizoctonia-disease suppression. Several plant-derived products (e.g., spent mushroom compost, dried algae, spent brewer’s grain, Brassica seed meal) were not effective. Lysobacter populations naturally present in the soil were increased 3–10 fold (measured by a TaqMan quantitative PCR) in soils amended with organic compounds that stimulated Rhizoctonia-disease suppression. The role of Lysobacter as a key factor in Rhizoctonia-disease suppression, however, could not be confirmed by adding Lysobacter isolates to a sterilized soil amended with yeast or chitin. Hence, we hypothesize that unexplored biological factors were involved in disease suppression, since the tested soil became conducive after gamma-sterilization. The consistent enhancement of Rhizoctonia-disease suppression in sugar beet with yeast and chitin amendments, and the efficacy of inexpensive protein-rich waste products such as feather meal and hoof meal in our bio-assays, warrants further study in field experiments.

Energy self-supply of large abattoir by sustainable waste utilization based on anaerobic mono-digestion

Abattoirs have a large number of energy intensive processes. Beside energy supply, disposal costs of animal by-products (ABP) are the main relevant cost drivers. In this study, successful implementation of a new waste and energy management system based on anaerobic digestion is described. Several limitations and technical challenges regarding the anaerobic digestion of the protein rich waste material had to be overcome. The most significant problems were process imbalances such as foaming and floatation as well as high accumulation of volatile fatty acids and low biogas yields caused by lack of essential microelements, high ammonia concentrations and fluctuation in operation temperature. Ultimately, 85% of the waste accumulated during the slaughter process is converted into 2700MWh thermal and 3200MWh electrical energy in a biogas combined heat and power (CHP) plant. The thermal energy is optimally integrated into the production process by means of a stratified heat buffer. The energy generated by the biogas CHP-plant can cover a significant share of the energy requirement of the abattoir corresponding to 50% of heat and 60% of electric demand, respectively. In terms of annual cost for energy supply and waste disposal a reduction of 63% from 1.4Mio€ to about 0.5Mio€ could be achieved with the new system. The payback period of the whole investment is approximately 9years. Beside the economic benefits also the positive environmental impact should be highlighted: a 79% reduction of greenhouse gas emissions from 4.5Miokg CO2 to 0.9Miokg CO2 annually was achieved. The realized concept received the Austrian Energy Globe Award and represents the first anaerobic mono-digestion process of slaughterhouse waste worldwide.

Mesophilic co-digestion of dairy manure and lipid rich solid slaughterhouse wastes: Process efficiency, limitations and floating granules formation

Lipid and protein rich solid slaughterhouse wastes are attractive co-substrates to increase volumetric biogas production in co-digestion with dairy manure. Addition of decanter sludge (DS), containing 42.2% of lipids and 35.8% of proteins (total solids basis), up to 5% of feed mixture resulted in a stable process without any indication of long chain fatty acids (LCFA) or free ammonia (NH3) inhibition and in 3.5-fold increase of volumetric biogas production. Contrary, only lipids addition as technical fat (TF) at over 2% of feed mixture resulted in formation of floating granules (FG) and process efficiency decrease. Formed FG had low biodegradability and its organic part was composed of lipids and calcium salts of LCFAs. Anaerobic digestion process intentionally directed to FG formation, could be a viable option for mitigation and control of lipids overload and derived LCFA inhibition.

Zeolites relieves inhibitory stress from high concentrations of long chain fatty acids

Protein and fat rich slaughterhouse waste is a very attractive waste stream for the production of biogas because of the high biochemical methane potential of the substrate. The material has however some drawbacks as the sole material for biogas production due to the production of several process disturbing metabolites such as ammonia, sulfides and long chain fatty acids. We can in this work present results that show that zeolites have the potential to relieve inhibitory stress from the presence of long chain fatty acids. Moreover, the results strongly indicate that it is mainly acetic acid consumers that are most negatively affected by long chain fatty acids and that the mechanism of stress relief is an adsorption of long chain fatty acids to the zeolites. In addition to this, it is shown that the effect is immediate and that only a small amount of zeolites is necessary to cancel the inhibitory effect of long chain fatty acids.

Effects of volumetric dilution on anaerobic digestion of food waste

Despite the increasing number of small scale digesters operating, there remains a lack of information with regards to performance optimization from an everyday user's standpoint. The objective of this study was to determine the effects of volumetric dilution and food waste composition on digester performance. Batch experiments utilizing food waste majoring in carbohydrate, protein, lipid, and cellulose, subjected to five concentrations of volumetric dilution (3.7%–17.1% total solids (TS)), were conducted. Irregardless of volumetric dilution, all assays achieved substrate degradation higher than 82.5% and did not suffer methanogenic inhibition, when provided with retention times comparable to those used in small scale digesters. Protein rich and cellulose rich waste achieved the highest methane potential varying between 0.410–0.539 m3/kg volatile solids (VS) and 0.450–0.535 m3/kg VS, respectively. Protein rich assays were also observed to be the first to achieve 50% of its Bo irregardless of concentrations, followed by carbohydrates and cellulose, and lipids having a considerably longer methanation time. Results saw an increase in total methane generated but a decrease in specific yield as % total solid increased. To successfully digest lipid rich waste a dilution no lesser than 1:4 was required.

Microwave-assisted synthesis of carbon nanodots through an eggshell membrane and their fluorescent application

Carbon nanodots (C-Dots) as a new form of carbonaceous nanomaterials have aroused much interest and intensive research due to their inspiring properties. Compared to traditional semiconductor quantum dots, these newly emergent nanodots possess a number of advantageous characteristics, among which low-toxicity is particularly fascinating. More and more research into C-Dots have focused on synthesis methods and biology-related applications. Microwave-assisted approaches have attracted attention because microwave treatment can provide intensive and efficient energy, and as a consequence shorten the reaction time. In this article, we designed a "green", rapid, eco-friendly and waste-reused approach to synthesize fluorescent and water-soluble C-Dots from eggshell membrane (ESM) ashes according to a microwave-assisted process. ESM selected as the carbon source was a common protein-rich waste in daily life and can be obtained easily and cheaply. The C-Dots from our method showed the maximal fluorescence emission peak at 450 nm and the fluorescence quantum yield was about 14%. We further designed a sensitive probe for glutathione based on the fluorescence turn off and on of the C-Dots-Cu(2+) system, which showed a linear range of 0.5-80 μmol L(-1) and detection limit of 0.48 μmol L(-1). In general, the C-Dots prepared briefly and inexpensively from ESM revealed excellent fluorescent property with promising potential for applications such as sample detection and biotechnology.

Cultivation of Pleurotus sajor-caju on banana stalk and Bahia grass based substrates

Banana stalks and Bahia grass were utilized as basic starting materials for the production of the mushroom Pleurotus sajor-caju. Banana stalks were combined with other waste or supplement products (wheat bran, coast-cross hay, bean straw and cotton textile mill) to obtain different nitrogen concentrations. Since Bahia grass is relatively rich in protein, it was combined with other substrates (banana stalk, coast-cross hay and bean straw) to maintain a substrate nitrogen concentration of about 1.5%. Banana stalks and Bahia grass were both more efficient in the production of the mushroom P. sajor-caju when utilized without the addition of other substrates, with biological efficiencies of 74.4% and 74.12%, respectively. When combined with other substrates or grasses, there was a drop in biological efficiency, independent of the concentration of nitrogen. Furthermore, the addition of protein-rich waste to banana stalks resulted in a decrease or absence of fructification, which indicates that high concentrations of nitrogen in the cultivation substrate may hinder the cultivation of this mushroom. On the other hand, results reveal that the ideal concentration of nitrogen may depend on other physicochemical factors and these factors may determine the success in cultivating P. sajor-caju. Therefore, we conclude that P. sajor-caju may be cultivated on banana stalk and Bahia grass as pure substrates, not being necessary their supplementation or combine them with another substrates.

Characterization of a keratinolytic protease produced by the feather-degrading Amazonian bacterium Bacillus sp. P45

An extracellular keratinolytic protease produced by Bacillus sp. P45 was purified and characterized. The keratinase had a molecular weight of approximately 26 kDa and was active over wide pH and temperature ranges, with optimal activity at 55°C and pH 8.0. However, this enzyme displayed low thermostability, being completely inactivated after 10 min at 50°C. Keratinase activity increased with Ca2+, Mg2+, Triton X-100, ethanol and DMSO, was stable in the presence of the reducing agent 2-mercaptoethanol, and was inactivated by SDS. PMSF (phenylmethylsulfonyl fluoride) completely inactivated and EDTA strongly inhibited the enzyme, indicating that the keratinase is a serine protease depending on metal ions for optimal activity and/or stability. Accordingly, analysis of tryptic peptides revealed sequence homologies which characterize the keratinase as a subtilisin-like serine protease. The purified enzyme was able to hydrolyze azokeratin and keratin azure. Casein was hydrolyzed at higher rates than keratinous substrates, and 2-mercaptoethanol tended to enhance keratin hydrolysis. With synthetic substrates, the keratinase showed a preference for aromatic and hydrophobic residues at the P1 position of tetrapeptides; the enzyme was not active, or the activity was drastically diminished, towards shorter peptides. Keratinase from Bacillus sp. P45 might potentially be employed in the production of protein hydrolysates at moderate temperatures, being suitable for the bioconversion of protein-rich wastes through an environmentally friendly process requiring low energy inputs.

Effect of protein on biohydrogen production from starch of food waste

This study demonstrated the influence of protein on biohydrogen production from carbohydrates, especially starch, by using different combinations of two model food wastes, rice as starch-rich and soybean residue as protein-rich food waste. It was found the maximum specific hydrogen production potential, 0.99 mol H2/mol initial starch as glucose, and the maximum specific hydrogen production rate, 530 ml H2/h g-VS, occurred at a starch/protein ratio of 1.7. The protein content in the initial food waste not only provided buffering capacity to neutralize the volatile fatty acids as concurrent products but also enhanced the hydrogen production by providing readily available organic nitrogen such as soluble proteins and amino acids to microorganisms.

Effects of nonionic surfactant on hydrolysis and fermentation of protein rich tannery solid waste

The untanned proteinaceous tannery solid waste, the animal fleshing (ANFL), was used as substrate in the treatment process (hydrolysis and fermentation) involving Synergistes sp. The nonionic surfactant (Tween 80) was evaluated for its ability to influence on microbial growth and enzyme activity in the hydrolysis and fermentation of ANFL. The addition of Tween 80 in the process significantly increased the activities of hydrolytic and fermentative enzymes like protease (338-360 Um l(-1)) and deaminase (187-206 Um l(-1)) compared to that of control (protease 195-220 Um l(-1) and deaminase 70-83 Um l(-1)). The total viable bacterial count was increased more than twofold, compared to the control in the presence of 0.15% Tween 80. The ANFL fermentation and formation of other metabolites were evidenced by Gas Chromatography and Mass Spectroscopy (GC-MS), Proton Nuclear Magnetic Resonance spectroscopy ((1)H NMR) and Fourier transform infra red spectroscopy (FT-IR). The breakdown of fibrillar proteins in ANFL was confirmed by the scanning electron microscopy (SEM) and the transmission electron microscopy (TEM).

Anaerobic digestion of secondary residuals from an anaerobic bioreactor at a brewery to enhance bioenergy generation

Many beer breweries use high-rate anaerobic digestion (AD) systems to treat their soluble high-strength wastewater. Biogas from these AD systems is used to offset nonrenewable energy utilization in the brewery. With increasing nonrenewable energy costs, interest has mounted to also digest secondary residuals from the high-rate digester effluent, which consists of yeast cells, bacteria, methanogens, and small (hemi)cellulosic particles. Mesophilic (37 degrees C) and thermophilic (55 degrees C) lab-scale, low-rate continuously-stirred anaerobic digestion (CSAD) bioreactors were operated for 258 days by feeding secondary residuals at a volatile solids (VS) concentration of approximately 40 g l(-1). At a hydraulic retention time (HRT) of 15 days and a VS loading rate of 2.7 g VS l(-1) day(-1), the mesophilic bioreactor showed an average specific volumetric biogas production rate of 0.88 l CH4 l(-1) day(-1) and an effluent VS concentration of 22.2 g VS l(-1) (43.0% VS removal efficiency) while the thermophilic bioreactor displayed similar performances. The overall methane yield for both systems was 0.21 l CH4 g(-1) VS fed and 0.47-0.48 l CH4 g(-1) VS removed. A primary limitation of thermophilic digestion of this protein-rich waste is the inhibition of methanogens due to higher nondissociated (free) ammonia (NH3) concentrations under similar total ammonium (NH4+) concentrations at equilibrium. Since thermophilic AD did not result in advantageous methane production rates or yields, mesophilic AD was, therefore, superior in treating secondary residuals from high-rate AD effluent. An additional digester to convert secondary residuals to methane may increase the total biogas generation at the brewery by 8% compared to just conventional high-rate digestion of brewery wastewater alone.

Optimised anaerobic treatment of house-sorted biodegradable waste and slaughterhouse waste in a high loaded half technical scale digester

Anaerobic co-digestion of organic wastes from households, slaughterhouses and meat processing industries was optimised in a half technical scale plant. The plant was operated for 130 days using two different substrates under organic loading rates of 10 and 12 kgCOD.m(-3).d(-1). Since the substrates were rich in fat and protein components (TKN: 12 g.kg(-1) the treatment was challenging. The process was monitored on-line and in the laboratory. It was demonstrated that an intensive and stable co-digestion of partly hydrolysed organic waste and protein rich slaughterhouse waste can be achieved in the balance of inconsistent pH and buffering NH4-N. In the first experimental period the reduction of the substrate COD was almost complete in an overall stable process (COD reduction >82%). In the second period methane productivity increased, but certain intermediate products accumulated constantly. Process design options for a second digestion phase for advanced degradation were investigated. Potential causes for slow and reduced propionic and valeric acid degradation were assessed. Recommendations for full-scale process implementation can be made from the experimental results reported. The highly loaded and stable codigestion of these substrates may be a good technical and economic treatment alternative.

Utilization of keratin-containing biowaste to produce biohydrogen

A two-stage fermentation system was constructed to test and demonstrate the feasibility of biohydrogen generation from keratin-rich biowaste. We isolated a novel aerobic Bacillus strain (Bacillus licheniformis KK1) that displays outstanding keratinolytic activity. The isolated strain was employed to convert keratin-containing biowaste into a fermentation product that is rich in amino acids and peptides. The process was optimized for the second fermentation step, in which the product of keratin fermentation--supplemented with essential minerals--was metabolized by Thermococcus litoralis, an anaerobic hyperthermophilic archaeon. T. litoralis grew on the keratin hydrolysate and produced hydrogen gas as a physiological fermentation byproduct. Hyperthermophilic cells utilized the keratin hydrolysate in a similar way as their standard nutrient, i.e., bacto-peptone. The generalization of the findings to protein-rich waste treatment and production of biohydrogen is discussed and possible means of further improvements are listed.

Single- and multi-component adsorption equilibria in bubble separation of organic materials.

Investigations were conducted on the adsorption equilibrium between the air bubbles and some organic materials in waste water. Langmuir's adsorption isotherm held for the adsorption of soluble or insoluble material in single-component solution or suspension, while the extended adsorption isotherm held in the multi-component system. Among organic materials tested, isoelectric protein coagula were most efficiently bubble-separated, although the efficiency of separation was greatly affected by the coexistence of soluble hydrophobic molecules due to competitive adsorption between coagulated protein and small hydrophobic molecules. Pretreatment was suggested of protein-rich waste water without the usual coagulants.