Glucoamylase production from food waste by Aspergillus niger under submerged fermentation

Evaluation of food wastes as a medium to produce chitin-glucan nanofiber from Aspergillus niger

This study investigated the potential of using food waste as a growth media for chitin-glucan nanofiber production by Aspergillus niger. For that purpose, a local hotel food waste was used to prepare four different media based on the protein and polysaccharide content of the waste. Optimal fermentation conditions, including medium composition, inoculum size of A. niger, incubation time, and shaking speed in biomass production, were determined using the 4 × 4 Taguchi experimental design. The characterization of produced chitin-glucan nanofiber was determined using FESEM, FT-IR, and NMR. The experimental design results showed that the highest amount of chitin-glucan nanofiber was found as 1.9 g/l at pH 5 and 30 °C with 58.82% yield. Optimal conditions for the highest yield were observed when the media containing 20% fruit-vegetable-rich waste, 30% protein-rich waste, and 50% polysaccharide-rich waste was used with an 8 mm inoculation size of A. niger at 6 d incubation time with 100 RPM shaking speed. Characterization studies have shown that chitin-glucan nanofibers obtained from wastes are equivalent to their commercial counterparts. The use of food wastes to produce chitin-glucan nanofiber from A. niger can save costs and significantly reduce environmental pollution.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-06088-9.

Recent Advances in Food Waste Transformations into Essential Bioplastic Materials

Lignocellulose is a major biopolymer in plant biomass with a complex structure and composition. It consists of a significant amount of high molecular aromatic compounds, particularly vanillin, syringeal, ferulic acid, and muconic acid, that could be converted into intracellular metabolites such as polyhydroxyalkanoates (PHA) and hydroxybutyrate (PHB), a key component of bioplastic production. Several pre-treatment methods were utilized to release monosaccharides, which are the precursors of the relevant pathway. The consolidated bioprocessing of lignocellulose-capable microbes for biomass depolymerization was discussed in this study. Carbon can be stored in a variety of forms, including PHAs, PHBs, wax esters, and triacylglycerides. From a biotechnology standpoint, these compounds are quite adaptable due to their precursors' utilization of hydrogen energy. This study lays the groundwork for the idea of lignocellulose valorization into value-added products through several significant dominant pathways.

Innovative Strategies for Upcycling Agricultural Residues and Their Various Pharmaceutical Applications

This review investigates innovative strategies for upcycling agricultural residues into valuable pharmaceutical compounds. The improper disposal of agricultural residues contributes to significant environmental issues, including increased greenhouse gas emissions and ecosystem degradation. Upcycling offers a sustainable solution, transforming these residues into high-value bioproducts (antioxidants, antitumor agents, antidiabetic compounds, anti-inflammatory agents, and antiviral drugs). Nanotechnology and microbial biotechnology have a crucial role in enhancing bioavailability and targeted delivery of bioactive compounds. Advanced techniques like enzymatic hydrolysis, green solvents, microwave processing, pyrolysis, ultrasonic processing, acid and alkaline hydrolysis, ozonolysis, and organosolv processes are explored for their effectiveness in breaking down agricultural waste and extracting valuable compounds. Despite the promising potential, challenges such as variability in residue composition, scalability, and high costs persist. The review emphasizes the need for future research on cost-effective extraction techniques and robust regulatory frameworks to ensure the safety, efficacy, and quality of bioproducts. The upcycling of agricultural residues represents a viable path towards sustainable waste management and production of pharmaceutical compounds, contributing to environmental conservation and public health improvements. This review provides an analysis of the current literature and identifies knowledge gaps, offering recommendations for future studies to optimize the use of agricultural residues in the drug industry.

Advanced anaerobic digestion of household food waste pretreated by in situ-produced mixed enzymes via solid-state fermentation: Feasibility and application perspectives

Enzymatic pretreatment is an effective method which can improve the anaerobic digestion (AD) efficiency of household food waste (HFW). As an alternative to expensive commercial enzymes, mixed enzymes (MEs) produced in situ from HFW by solid-state fermentation (SSF) can greatly promote the hydrolysis rate of HFW and achieve advanced anaerobic digestion (AAD) economically sustainable. In this paper, strategies for improving the efficiency of the enzyme-production process and the abundance of MEs are briefly discussed, including SSF, fungal co-cultivation, and stepwise fermentation. The feasibility of using HFW as an applicable substrate for producing MEs (amylase, protease, and lignocellulose-degrading enzymes) and its potential advantages in HFW anaerobic digestion are comprehensively illustrated. Based on the findings, an integrated AAD process of HFW pretreated with MEs produced in situ was proposed to maximise bioenergy recovery. The mass balance results showed that the total volatile solids removal rate could reach 98.56%. Moreover, the net energy output could reach 2168.62 MJ/t HFW, which is 9.79% higher than that without in situ-produced MEs and pretreatment. Finally, perspectives for further study are presented.

Aspergillus clavatus UEM 04: An efficient producer of glucoamylase and α-amylase able to hydrolyze gelatinized and raw starch

The best amylolytic activity production by Aspergillus clavatus UEM 04 occurred in submersed culture, with starch, for 72 h, at 25 °C, and 100 rpm. Exclusion chromatography partially purified two enzymes, which ran as unique bands in SDS-PAGE with approximately 84 kDa. LC-MS/MS identified a glucoamylase (GH15) and an α-amylase (GH13_1) as the predominant proteins and other co-purified proteins. Zn2+, Cu2+, and Mn2+ activated the glucoamylase, and SDS, Zn2+, Fe3+, and Cu2+ inhibited the α-amylase. The α-amylase optimum pH was 6.5. The optimal temperatures for the glucoamylase and α-amylase were 50 °C and 40 °C, and the Tm was 53.1 °C and 56.3 °C, respectively. Both enzymes remained almost fully active for 28-32 h at 40 °C, but the α-amylase thermal stability was calcium-dependent. Furthermore, the glucoamylase and α-amylase KM for starch were 2.95 and 1.0 mg/mL, respectively. Still, the Vmax was 0.28 μmol/min of released glucose for glucoamylase and 0.1 mg/min of consumed starch for α-amylase. Moreover, the glucoamylase showed greater affinity for amylopectin and α-amylase for maltodextrin. Additionally, both enzymes efficiently degraded raw starch. At last, glucose was the main product of glucoamylase, and α-amylase produced mainly maltose from gelatinized soluble starch hydrolysis.

Trends and challenges in the valorization of kitchen waste to polyhydroxyalkanoates

Kitchen waste (KW) is frequently available for free or with a negative cost due to its huge production. It contains a large proportion of organic substances, especially fermentable sugars, which can be used for bioplastic (polyhydroxyalkanoates or PHA) synthesis. Nevertheless, due to the difficulties in processing, various pre-treatments of KW are being investigated to enhance the concentration of simple sugars released during its hydrolysis. The effective use of KW will help in minimizing the issues of its inappropriate disposal. However, the review on KW to bioplastic synthesis is rarely reported in the literature. Hence, this particular review provides a comprehensive summary of the updated research developments in KW valorization and its potency as a feedstock for PHAs synthesis. Additionally, the impacts of KW, its availability, the necessary pre-treatments for the biopolymerization process, as well as the prospects and challenges for industrially generating sustainable PHAs, are critically discussed.

Novel Approaches in the Valorization of Agricultural Wastes and Their Applications

Worldwide, a huge amount of agricultural food wastes and byproducts containing valuable bioactive compounds are generated, especially throughout the entire supply chain. Minimizing food wastes and byproducts is the first option to avoid environmental problems, and to help the economy and the society. Although many countries implement policies to reduce food wastes and byproducts, and different management methods are available to utilize agricultural food wastes, they are still produced annually. Nanotechnological and biotechnological approaches are recently used as novel and green applications to valorize agricultural food wastes and improve their stability and applicability. In this Review, these approaches are covered in detail with given examples. Another valorization way of consumable food waste is using it for functional food production. This Review focuses on specific examples of functional foods with food waste as an ingredient. In addition, the problems and limitations of waste management and valorization methods are investigated, considering future perspectives.

The glucoamylase from Aspergillus wentii: Purification and characterization

This study describes for the first time the purification and characterization of a glucoamylase from Aspergillus wentii (strain PG18), a species of the Aspergillus genus Cremei section. Maximum enzyme production (∼3.5 U/ml) was obtained in submerged culture (72 h) with starch as the carbon source, at 25°C, and with orbital agitation (100 rpm). The enzyme was purified with one-step molecular exclusion chromatography. The 86 kDa purified enzyme hydrolyzed starch in a zymogram and had activity against p-nitrophenyl α- d-glucopyranoside. The optimal enzyme pH and temperature were 5.0 and 60°C (at pH 5.0), respectively. The T_m of the purified enzyme was 60°C, at pH 7.0. The purified glucoamylase had a K_M for starch of 1.4 mg/ml and a V_max of 0.057 mg/min of hydrolyzed starch. Molybdenum activated the purified enzyme, and sodium dodecyl sulfate inhibited it. A thin layer chromatography analysis revealed glucose as the enzyme's main starch hydrolysis product. An enzyme's peptide sequence was obtained by mass spectrometry and used to retrieve a glucoamylase within the annotated genome of A. wentii v1.0. An in silico structural model revealed a N-terminal glycosyl hydrolases family 15 (GH15) domain, which is ligated by a linker to a C-terminal carbohydrate-binding module (CBM) from the CBM20 family.

Oriented Fermentation of Food Waste towards High-Value Products: A Review

Food waste has a great potential for resource recovery due to its huge yield and high organic content. Oriented fermentation is a promising method with strong application prospects due to high efficiency, strong robustness, and high-value products. Different fermentation types lead to different products, which can be shifted by adjusting fermentation conditions such as inoculum, pH, oxidation-reduction potential (ORP), organic loading rate (OLR), and nutrients. Compared with other types, lactic acid fermentation has the lowest reliance on artificial intervention. Lactic acid and volatile fatty acids are the common products, and high yield and high purity are the main targets of food waste fermentation. In addition to operational parameters, reactors and processes should be paid more attention to for industrial application. Currently, continuously stirred tank reactors and one-stage processes are used principally for scale-up continuous fermentation of food waste. Electro-fermentation and iron-based or carbon-based additives can improve food waste fermentation, but their mechanisms and application need further investigation. After fermentation, the recovery of target products is a key problem due to the lack of green and economic methods. Precipitation, distillation, extraction, adsorption, and membrane separation can be considered, but the recovery step is still the most expensive in the entire treatment chain. It is expected to develop more efficient fermentation processes and recovery strategies based on food waste composition and market demand.

Pulp wash: a new source for production of ligninolytic enzymes and biomass and its toxicological evaluation after biological treatment

Pulp wash was used as substrate for the activity of ligninolytic enzymes of the fungus Pleurotus sajor-caju. Activity of laccase (Lac) and manganese peroxidase (MnP) as well as fungal biomass occurred under four conditions: different pulp wash concentrations, pH variation at the optimal pulp wash concentration, different glucose concentrations, and different concentrations of ammonium nitrate. The best enzyme activity and biomass production were obtained with in natura pulp wash and pH corrected to 5.0 (4884 IU/L Lac; 82 IU/L MnP; 25 g/100 mL biomass). However, the addition of glucose and ammonium nitrate to the pulp wash was not necessary for increasing the enzyme activity and biomass production. Efficient removal of pulp wash chemical oxygen demand (99.66%) and biochemical oxygen demand (83.27%) occurred after the mycoremediation with P. sajor-caju in the optimized conditions. Lactuca sativa L. seeds germination bioassay showed a four-fold reduction in the residue toxicity (EC₅₀ 28.72%) after the treatment with the fungus. Our findings are consistent with the notion that pulp wash is an excellent substrate for inducing the activity of ligninolytic enzymes and producing fungal biomass, and that the biological treatment is efficient to reduce effluent toxicity.

Bioconversion of kitchen wastes into bioflocculant and its pilot-scale application in treating iron mineral processing wastewater

In this study, the feasibility of converting kitchen waste into bioflocculant using Bacillus agaradhaerens C9 was analyzed. The result showed that strain C9 could secrete various degrading enzymes, including amylase, protease, lipase, cellulase, xylanase and pectinase, promoting the hydrolysis of kitchen waste. Strong alkaline fermentation condition was able to induce the bioflocculant production, and inhibit the growth of contaminated bacteria, which avoids the sterilization process of kitchen waste. The optimum fermentation condition for enzymatic hydrolysis and bioflocculant production was 40 g/L kitchen waste, 37 °C, pH 9.5, and the highest bioflocculant yield of 6.92 g/L was achieved. Furthermore, bioflocculant was applied to treat pilot-scale (30 L) of mineral processing wastewater for the first time, and the removal rate of 92.35% was observed when 9 mg/L bioflocculant was added into wastewater. Therefore, this study could promote the resource utilization of kitchen waste and recycling of mineral processing wastewater.

Exploration of a high-efficiency and low-cost technique for maximizing the glucoamylase production from food waste

This study was aimed at the exploration of high-efficiency and low-cost technique for glucoamylase (GA) production from food waste; moreover, the produced GA could be directly used in the hydrolysis of food waste. A mixture of food waste, rice waste and cake waste as a sole feedstock was investigated for the production of GA via solid-state fermentation. The highest GA activity of 458.3 U g-1 was obtained from the rice waste after 9 days of incubation. The cake waste also demonstrated a high GA production, achieving 406.5 U g-1 dry substrate. However, the most practical substrate for GA production that could be integrated in the food waste treatment was the mixed food waste, which could effectively produce GA without any additives or adjustments using the technique developed in this study. The optimum conditions for GA production from the mixed food waste were determined through a response surface methodology: the temperature of 31.16 °C, the inoculum amount of 1.54 mL, and the time of fermentation of 7.81 days. The maximum GA activity of 180.59 U g-1 could be achieved under these optimum conditions, which was actually much higher than those reported in the literature. This study showed that the mixed food waste could be an ideal feedstock for the on-site production of high-activity GA, and the produced GA could be directly applied in food waste hydrolysis, which significantly reduced the process cost.

Some physico-chemical and thermodynamic characteristics of maize starches hydrolyzed by glucoamylase

Glucoamylolysis of maize starch at 55 °C has been studied by means of scanning electron microscopy (SEM), wide-angle X-ray diffraction spectroscopy (WAXD), and differential scanning calorimetry (DSC). It was found that hydrolysis is accompanied by changes in thermodynamic parameters of diluted aqueous dispersions of partially hydrolyzed starches. Such changes are ensured by two processes directly from hydrolysis and accompanying annealing. At relatively low degrees of hydrolysis (less than 30%), changes in thermodynamic parameters are mainly controlled by annealing. At the same time, at high degrees of hydrolysis (more than 40%), the main contribution to changes in thermodynamic parameters of partially hydrolyzed starch granules is due to the hydrolysis itself. It has been established that the main controlling parameter is the thickness of crystalline lamellae L_crl, which, when annealed, increases, but tends to decrease at deeper glucoamylolisis. It has been established that the thickness L_crl of crystalline lamellae, which increases with annealing, but shows a tendency to decrease with deeper glucoamylolysis is the most representative parameter of changes in maize starch after hydrolysis.

Strain selection and medium optimization for glucoamylase production from industrial potato waste by Aspergillus niger

BACKGROUND

Glucoamylase is one of the most common enzymes used in the food industry to break down starch into its monomers. Glucoamylase production and its activity are highly dependent on medium composition. Starch is well known as a glucoamylase inducer, and utilization of industrial starchy potato waste is an inexpensive way of improving glucoamylase production. Since glucoamylase production is highly dependent on medium composition, in this study medium optimization for glucoamylase production was considered to enhance glucoamylase activity.

RESULTS

Among the evaluated microbial species, Aspergillus niger van Tieghem was found to be the best glucoamylase-producing fungus. The Plackett-Burman design was used to screen various medium ingredients, and malt extract, FeSO4 .7H2 O and CaCl2 ·2H2 O were found to have significant effects on glucoamylase production. Finally, malt extract, FeSO4 .7H2 O and CaCl2 .2H2 O were optimized by using a central composite design of response surface methodology. The results showed that the optimal medium composition for A. niger van Tieghem was 50 g L(-1) industrial waste potato mash supplemented with 51.82 g L(-1) malt extract, 9.27 g L(-1) CaCl2 ·2H2 O and 0.50 g L(-1) FeSO4 .7H2 O.

CONCLUSION

At the end of optimization, glucoamylase activity and glucose production were improved 126% and 98% compared to only industrial waste potato mash basal medium; 274.4 U mL(-1) glucoamylase activity and 41.7 g L(-1) glucose levels were achieved, respectively. © 2015 Society of Chemical Industry.

Enhanced fermentable sugar production from kitchen waste using various pretreatments

The kitchen waste fraction in municipal solid waste contains high organic matter particularly carbohydrate that can contribute to fermentable sugar production for subsequent conversion to bioethanol. This study was carried out to evaluate the influence of single and combination pretreatments of kitchen waste by liquid hot water, mild acid pretreatment of hydrochloric acid (HCl) and sulphuric acid (H2SO4) and enzymatic hydrolysis (glucoamylase). The maximum total fermentable sugar produced after combination pretreatment by 1.5% HCl and glucoamylase consisted of 93.25 g/L glucose, 0.542 g/L sucrose, 0.348 g/L maltose, and 0.321 g/L fructose. The glucose released by the combination pretreatment method was 0.79 g glucose/g KW equivalent to 79% of glucose conversion. The effects of the pre-treatment on kitchen waste indicated that the highest solubilization was 40% by the combination method of 1.5% HCl and glucoamylase. The best combination pre-treatment gave concentrations of lactic acid, acetic acid, and propionic acid of 11.74 g/L, 6.77 g/L, and 1.02 g/L, respectively. The decrease of aliphatic absorbance bands of polysaccharides at 2851 and 2923 cm(-1) and the increase on structures of carbonyl absorbance bands at 1600 cm(-1) reflects the progress of the kitchen waste hydrolysis to fermentable sugars. Overall, 1.5% HCl and glucoamylase treatment was the most profitable process as the minimum selling price of glucose was USD 0.101/g kitchen waste. Therefore, the combination pretreatment method was proposed to enhance the production of fermentable sugar, particularly glucose from kitchen waste as the feedstock for bioethanol production.

Fungal hydrolysis in submerged fermentation for food waste treatment and fermentation feedstock preparation

Potential of fungal hydrolysis in submerged fermentation by Aspergillus awamori and Aspergillus oryzae as a food waste treatment process and for preparation of fermentation feedstock has been investigated. By fungal hydrolysis, 80-90% of the initial amount of waste was reduced and degraded within 36-48 h into glucose, free amino nitrogen (FAN) and phosphate. Experiments revealed that 80-90% of starch can be converted into glucose and highest concentration of FAN obtained, when solid mashes of A. awamori and A. oryzae are successively added to fermentations at an interval of 24h. A maximal solid-to-liquid ratio of 43.2% (w/v) of food waste has been tested without a negative impact on releases of glucose, FAN and phosphate, and final concentrations of 143 g L(-1), 1.8 g L(-1) and 1.6 g L(-1) were obtained in the hydrolysate, respectively. Additionally, fungal hydrolysis as an alternative to conventional treatments for utilization of food waste is discussed.

Production of fungal glucoamylase for glucose production from food waste

The feasibility of using pastry waste as resource for glucoamylase (GA) production via solid state fermentation (SSF) was studied. The crude GA extract obtained was used for glucose production from mixed food waste. Our results showed that pastry waste could be used as a sole substrate for GA production. A maximal GA activity of 76.1 ± 6.1 U/mL was obtained at Day 10. The optimal pH and reaction temperature for the crude GA extract for hydrolysis were pH 5.5 and 55 °C, respectively. Under this condition, the half-life of the GA extract was 315.0 minutes with a deactivation constant (kd) 2.20 × 10-3minutes-1. The application of the crude GA extract for mixed food waste hydrolysis and glucose production was successfully demonstrated. Approximately 53 g glucose was recovered from 100 g of mixed food waste in 1 h under the optimal digestion conditions, highlighting the potential of this approach as an alternative strategy for waste management and sustainable production of glucose applicable as carbon source in many biotechnological processes.

Optimization of ethanol, citric acid, and α-amylase production from date wastes by strains of Saccharomyces cerevisiae, Aspergillus niger, and Candida guilliermondii

The present study deals with submerged ethanol, citric acid, and α-amylase fermentation by Saccharomyces cerevisiae SDB, Aspergillus niger ANSS-B5, and Candida guilliermondii CGL-A10, using date wastes as the basal fermentation medium. The physical and chemical parameters influencing the production of these metabolites were optimized. As for the ethanol production, the optimum yield obtained was 136.00 ± 0.66 g/l under optimum conditions of an incubation period of 72 h, inoculum content of 4% (w/v), sugars concentration of 180.0 g/l, and ammonium phosphate concentration of 1.0 g/l. Concerning citric acid production, the cumulative effect of temperature (30°C), sugars concentration of 150.0 g/l, methanol concentration of 3.0%, initial pH of 3.5, ammonium nitrate concentration of 2.5 g/l, and potassium phosphate concentration of 2.5 g/l during the fermentation process of date wastes syrup did increase the citric acid production to 98.42 ± 1.41 g/l. For the production of α-amylase, the obtained result shows that the presence of starch strongly induces the production of α-amylase with a maximum at 5.0 g/l. Among the various nitrogen sources tested, urea at 5.0 g/l gave the maximum biomass and α-amylase estimated at 5.76 ± 0.56 g/l and 2,304.19 ± 31.08 μmol/l/min, respectively after 72 h incubation at 30°C, with an initial pH of 6.0 and potassium phosphate concentration of 6.0 g/l.