Stepwise optimisation of enzyme production in solid state fermentation of waste bread pieces

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.

A systematic review on garbage enzymes and their applications in environmental processes

Understanding the new insight on conversion of organic waste into value-added products can improve the environmental activities driven by microorganisms and return the nutrients to environment and earth. Here, we comprehensively review the available knowledge on application of garbage enzyme (GE) for different environmental activities including waste activated sludge, composting process, landfill leachate treatment, soil remediation and wastewater treatment with special focus on their efficiency. To identify peer-reviewed studies published in English-language journals, a comprehensive search was performed across multiple electronic databases including Scopus, Web of Science, Pubmed, and Embase. The search was conducted systematically using relevant keywords. The eligible studies were analyzed to extract data and information pertaining to components of GE, fermentation process operational parameters, type of hydrolytic enzymes and improved environmental performance. The findings derived from this current review demonstrated that GE produced from the fruit and vegetable peels, molasses or brown sugar (carbon source), and water within fermentation process contain different hydrolytic enzymes in order to facilitate the organic waste degradation. Therefore, GE can be considered as a promising and efficient pathway in order to improve the environmental activities depended on microorganism including, composting, wastewater and leachate treatment and bioremediation process.

Feasibility study for estimating optimal substrate parameters for sustainable green roof in Sri Lanka

In twenty-first century buildings, green roof systems are envisioned as great solution for improving Environmental sustainability in urban ecosystems and it helps to mitigate various health hazards for humans due to climatic pollution. This study determines the feasibility of using five domestic organic wastes, including sawdust, wood bark, biochar, coir, and compost, as sustainable substrates for green roofs as compared to classical Sri Lankan base medium (fertiliser + potting mix) in terms of physicochemical and biological parameters associated with growing mediums. Comprehensive methodologies were devised to determine the thermal conductivity and electric conductivity of growing mediums. According to preliminary experimental results, the most suitable composition for green roof substrates comprised 60% organic waste and 40% base medium. Sawdust growing medium exhibited the highest moisture content and minimum density magnitudes. Biochar substrate was the best performing medium with the highest drought resistance and vegetation growth. The wood bark substrate had the highest thermal resistance. Growing mediums based on compost, sawdust, and coir produced the best results in terms of nitrate, phosphate, pH, and electric conductivity (EC) existence. This study provided a standard set of comprehensive comparison methodologies utilising physicochemical and biological properties required for substrate characterization. The findings of this research work have strong potential in the future to be used in selecting the most suitable lightweight growing medium for a green roof based on stakeholder requirements.

Bread Surplus: A Cumulative Waste or a Staple Material for High-Value Products?

Food waste has been widely valorized in the past years in order to develop eco-friendly materials. Among others, bread waste is currently of increasing interest, as it is considered a huge global issue with serious environmental impacts and significant economic losses that have become even greater in the post-pandemic years due to an increase in cereal prices, which has led to higher production costs and bread prices. Owing to its richness in polysaccharides, bread waste has been previously studied for its physico-chemical characteristics and its numerous biotechnological applications. The present review highlights the re-use of bread waste and its valorization as a valuable resource by making value-added products through numerous technological processes to increase efficiency at all stages. Many research studies reporting several transformation methods of surplus bread into ethanol, lactic acid, succinic acid, biohydrogen, hydroxymethylfurfural, proteins and pigments, glucose-fructose syrup, aroma compounds, and enzymes are widely discussed. The wide variety of suggested applications for recycling bread waste provides significant insights into the role of technology development in potentially maximizing resource recovery and consequently contributing to environmental performance by reducing the amount of bread waste in landfills.

High-Efficiency Conversion of Bread Residues to Ethanol and Edible Biomass Using Filamentous Fungi at High Solids Loading: A Biorefinery Approach

Bread residues represent a significant fraction of retail food wastes, becoming a severe environmental challenge and an economic loss for the food sector. They are, however, an attractive resource for bioconversion into value-added products. In this study, the edible filamentous fungi Neurospora intermedia and Aspergillus oryzae were employed for the production of bioethanol and high-protein biomass by cultivation on enzymatically liquefied bread-waste medium at 150 g/L solids. The fermentation of hydrolysate by N. intermedia resulted in the ethanol titer of 32.2 g/L and biomass yield of 19.2 g/L with ca. 45% protein. However, the fermentation ended with a considerable amount of residual fermentable sugars; therefore, the liquid medium after the first fermentation was distilled and fermented again by two fungal strains (N. intermedia and A. oryzae). The fermentations resulted in the production of additional ethanol and biomass. A. oryzae showed better performance in the production of biomass, while the other strain yielded more ethanol. The final products’ yield ranged 0.29–0.32 g EtOH/g and 0.20–0.22 g biomass/g bread waste depending on the strain used in the second fermentation. The study shows that valorization of bread residuals by fungi is a promising option for the production of biofuels and foodstuff within the circular bioeconomy approach.

Biovalorization of Market Surplus Bread for Development of Probiotic-Fermented Potential Functional Beverages

Bread wastage is a growing concern in many developed countries. This research aimed to explore the biovalorization of market surplus bread for the development of probiotic-fermented beverages in a zero-waste approach. Bread slurries with different initial total solid contents were inoculated with probiotics Lacticaseibacillus rhamnosus GG (LGG) and Saccharomyces cerevisiae CNCM I-3856, alone and in combination. Our results showed that, of all percentages tested, 5% (w/w, dry weight) initial total solid content resulted in better growth of the probiotics and higher cell counts, while the texture of bread slurries with concentrations higher than 5.0% was too thick and viscous for bread beverage developments. In addition, the development of probiotic-fermented bread beverages was feasible on various types of bread. Furthermore, food additives (sweetener and stabilizer) did not affect the growth of LGG and S. cerevisiae CNCM I-3856 in both mono- and co-culture fermentation. During shelf life measurement, co-inoculation of LGG with S. cerevisiae CNCM I-3856 significantly improved the survival of LGG compared to the mono-culture at 5 and 30 °C, demonstrating the protective effects provided by the yeast. Our study suggests the potential of using market surplus bread as raw materials to deliver live probiotics with sufficient cell counts.

Recycling bread waste into chemical building blocks using a circular biorefining approach

Food waste is a global problem, causing significant environmental harm and resulting in substantial economic losses globally. Bread is the commonly wasted food item in the developed world and presents a severe problem for the majority of European nations. It is the second most wasted food item in the UK after potatoes, with an equivalent of 20 million slices of bread thrown away daily. Bread is a starchy material and a rich and clean source of easily extractable fermentable sugars - this is in direct contrast to lignocellulosic feedstocks where harsh physical, chemical and/or enzymatic pretreatment processes are required for release of fermentable sugars. Furthermore, these necessary lignocellulosic pretreatment methods often produce sugars contaminated with fermentation inhibitors. Therefore, bread waste presents a clear opportunity as a potential carbon source for novel commercial processes and, to this end, several alternative routes have been developed to utilize bread waste. Possibilities for direct recycling of bread waste within the food industry are limited due to the relatively short material lifetime, stringent process and hygiene requirements. Anaerobic digestion (AD) and incineration are commonly employed methods for the valorisation of bread waste, generating limited amounts of green energy but with little other environmental or economic benefits. Most food wastes and by-products in the UK including bakery waste are treated through AD processes that fail to harness the full potential of the these wastes. This short communication reviews the challenges of handling bread waste, with a focus on a specific UK scenario. The review will consider how bread waste is generated across the supply chain, current practices to deal with the waste and logistics challenges in waste collection. The presence of clean and high-quality fermentable sugars, proteins and other nutrients in bread make it an ideal substrate for generating chemicals, fuels, bioplastics, pharmaceuticals and other renewable products through microbial fermentations. We suggest potential applications for recycling bread waste into its chemical building blocks through a fermentative route where a circular biorefining approach could maximize resource recovery and environmental savings and eliminate waste to as close to zero as possible.

Integration of Solid State and Submerged Fermentations for the Valorization of Organic Municipal Solid Waste

Solid state fermentation (SsF) is recognized as a suitable process for the production of enzymes using organic residues as substrates. However, only a few studies have integrated an evaluation of the feasibility of applying enzymes produced by SsF into subsequent hydrolyses followed by the production of target compounds, e.g., lactic acid (LA), through submerged-liquid fermentations (SmF). In this study, wheat bran (WB) was used as the substrate for the production of enzymes via SsF by Aspergillus awamori DSM No. 63272. Following optimization, cellulase and glucoamylase activities were 73.63 ± 5.47 FPU/g_ds and 107.10 ± 2.63 U/g_db after 7 days and 5 days of fermentation, respectively. Enzymes were then used for the hydrolysis of the organic fraction of municipal solid waste (OFMSW). During hydrolysis, glucose increased considerably with a final value of 19.77 ± 1.56 g/L. Subsequently, hydrolysates were fermented in SmF by Bacillus coagulans A166 increasing the LA concentration by 15.59 g/L. The data reported in this study provides an example of how SsF and SmF technologies can be combined for the valorization of WB and OFMSW.

Valorization of Bread Waste to a Fiber- and Protein-Rich Fungal Biomass

Filamentous fungi can be used for the valorization of food waste as a value-added product. The goal of this study was the valorization of bread waste through fungal cultivation and the production of value-added products. The fungal cultivation was verified for upscaling from shake flasks to a bench-scale bioreactor (4.5 L) and a pilot-scale bioreactor (26 L). The fungus showed the ability to grow without any additional enzymes or nutrients, and it was able to consume a bread concentration of 4.5% (w/v) over 48 h. The biomass concentration in the shake flasks was 4.1 g/L at a 2.5% bread concentration, which increased to 22.5 g/L at a 15% bread concentration. The biomass concentrations obtained after 48 h of cultivation using a 4.5% bread concentration were 7.2–8.3 and 8.0 g/L in 4.5 and 26 L bioreactors, respectively. Increasing the aeration rate in the 4.5 L bioreactor decreased the amount of ethanol produced and slightly reduced the protein content of the fungal biomass. The initial protein value in the bread was around 13%, while the protein content in the harvested fungal biomass ranged from 27% to 36%. The nutritional value of the biomass produced was evaluated by analyzing the amino acids and fatty acids. This study presents the valorization of bread waste through the production of a protein- and fatty-acid-rich fungal biomass that is simultaneously a source of microfibers.

From stale bread and brewers spent grain to a new food source using edible filamentous fungi

By-products from the food sector with a high load of organic matter present both a waste-handling problem related to expenses and to the environment, yet also an opportunity. This study aims to increase the value of stale bread and brewers spent grain (BSG) by re-introducing these residues to the food production chain by converting them to new protein-enriched products using the edible filamentous fungi Neurospora intermedia and Rhizopusoryzae. After 6 days of solid state fermentation (at 35°C, with a95% relative humidity and moisture content of 40% in the substrate) on stale bread, a nutrient-rich fungal-fermented product was produced. The total protein content, as analyzed by total amino acids, increased from 16.5% in stale sourdough bread to 21.1% (on dry weight basis) in the final product with an improved relative ratio of essential amino acids. An increase in dietary fiber, minerals (Cu, Fe, Zn) and vitamin E, as well as an addition of vitamin D2 (0.89 µg/g dry weight sample) was obtained compared with untreated stale bread. Furthermore, addition of BSG to the sourdough bread with the aim to improve textural changes after fermentation showed promising outcomes. Cultivation of N. intermedia or R. oryzae on stale sourdough bread mixed with 6.5% or 11.8% BSG, respectively, resulted in fungal-fermented products with similar textural properties to a commercial soybean burger. Bioconversion of stale bread and BSG by fungal solid state fermentation to produce a nutrient-enriched food product was confirmed to be a successful way to minimize food waste and protein shortage.

The effect of the stale bread flour addition on flour and bread quality

In this study, the effect of the flour, which was obtained from stale bread, on flour and bread quality was investigated. The bread that was staled at refrigerator for 7 days was prepared as whole and crumb, and was grinded to convert into flour. The staled whole and crumb bread flours were stored at −18 °C and used to replace 0, 15, 30 and 45% of wheat flour. Then microbiological and physicochemical properties of flours; physical, textural and sensory properties of bread obtained from these composite flours were investigated. We concluded that stale bread flour could be used for bread production at the level of 15%. If the total bread production and consumption is considered, this addition level could provide a significant amount of waste bread recycling each year.

Efficient two-step lactic acid production from cassava biomass using thermostable enzyme cocktail and lactic acid bacteria: insights from hydrolysis optimization and proteomics analysis

Lactic acid is an intermediate-volume specialty chemical, used in the production of biodegradable polymers and other chemicals. Although lactic acid production process is well established, however, the cost of production is very high. Therefore, in this study; starchy biomass (cassava) was hydrolyzed with in-house enzyme cocktail prepared from Aspergillus foetidus MTCC508 and Bacillus subtilis RA10. Process optimization using Taguchi experimental design helped to optimize the most effective ratio of fungal and bacterial amylase for effective saccharification of cassava. A higher sugar yield of 379.63 mg/gds was obtained under optimized conditions, using 30 U/gds of bacterial enzyme and 90 U/gds of the fungal enzyme at pH 4 within 48 h of saccharification. Among 11 lactic acid bacteria isolated, Lactobacillus fermentum S1A and Lactobacillus farraginis SS3A produced the highest amount of lactic acid 0.81 g/g and 0.77 g/g, respectively, from the cassava hydrolysate. The study proved the potential renewable source of cassava biomass as a source for fermentable sugars that can be fermented to lactic acid with high yield. In future, this cost-effective and environmental-friendly bioprocess can be upscaled for industrial lactic acid production.

Optimization of Protease and Amylase Production by Rhizopus oryzae Cultivated on Bread Waste Using Solid-State Fermentation

This research was carried for the coproduction of two industrial enzymes: α-amylase and protease via SSF by Rhizopus oryzae on humidified bread waste. Fermentation time, inoculum size, initial moisture content, salt solutions, and the thickness of the substrate were investigated one by one. Fungus culture was carried out in sterile aluminum trays, and pH was adjusted to 5.5. The main results showed that the highest levels of enzyme production were obtained at 120 h, 65% relative humidity, height media of 1 cm, 105 spore/g, and M-9 solution (g/L): NaH2PO4, 12.8; KH2PO4, 3; NaCl, 0.5; NH4Cl, 1; MgSO4 7H2O, 0.5; CaCl2 2H2O, 0.01. α-Amylase (100 U/g) and protease (2400 U/g) produced by SSF from Rhizopus oryzae (CH4) on BW as substrate are of great interest in industries and could be valorized as enhancers of the bread making process.

Combining submerged and solid state fermentation to convert waste bread into protein and pigment using the edible filamentous fungus N. intermedia

Waste streams from ethanol and bread production present inexpensive, abundant and underutilized renewable substrates that are highly available for valorisation into high-value products. A combined submerged to solid state fermentation strategy was studied using the edible filamentous fungus Neurospora intermedia to biotransform ethanol plant residues 'thin stillage' and waste bread as substrates for the production of additional ethanol, biomass and a feed product rich in pigment. The fungus was able to degrade the stillage during submerged fermentation, producing 81 kg ethanol and 65 kg fungal biomass per ton dry weight of thin stillage. Concurrently, the second solid state fermentation step increased the protein content in waste bread by 161%. Additionally, 1.2 kg pigment per ton waste bread was obtained at the best conditions (6 days solid state fermentation under light at 95% relative humidity at 35 °C with an initial substrate moisture content of 40% using washed fungal biomass to initiate fermentation). This study presents a means of increasing the value of waste bread while reducing the treatment load on thin stillage in ethanol plants.

The Development of a Sorghum Bran-Based Biorefining Process to Convert Sorghum Bran into Value Added Products

Sorghum bran, a starch rich food processing waste, was investigated for the production of glucoamylase in submerged fungal fermentation using Aspergillus awamori. The fermentation parameters, such as cultivation time, substrate concentration, pH, temperature, nitrogen source, mineral source and the medium loading ratio were investigated. The glucoamylase activity was improved from 1.90 U/mL in an initial test, to 19.3 U/mL at 10% (w/v) substrate concentration, pH 6.0, medium loading ratio of 200 mL in 500 mL shaking flask, with the addition of 2.5 g/L yeast extract and essential minerals. Fermentation using 2 L bioreactors under the optimum conditions resulted in a glucoamylase activity of 23.5 U/mL at 72 h, while further increase in sorghum bran concentration to 12.5% (w/v) gave an improved gluco-amylase activity of 37.6 U/mL at 115 h. The crude glucoamylase solution was used for the enzymatic hydrolysis of the sorghum bran. A sorghum bran hydrolysis carried out at 200 rpm, 55 °C for 48 h at a substrate loading ratio of 80 g/L resulted in 11.7 g/L glucose, similar to the results obtained using commercial glucoamylase. Large-scale sorghum bran hydrolysis in 2 L bioreactors using crude glucoamylase solution resulted in a glucose concentration of 38.7 g/L from 200 g/L sorghum bran, corresponding to 94.1% of the theoretical hydrolysis yield.

Conversion of food and kitchen waste to value-added products

Food and kitchen waste - omnipresent in every corner of the world serve as an excellent source of value added products owing to high organic content. Regardless of existence of various traditional methods of land filling or biogas production used to harness food waste energy, effective conversion of food to valuable resources is often challenged by its heterogenous nature and high moisture content. The current paper tries to lay down the prospects and consequences associated with food waste management. The various social, economical and environmental concerns associated with food waste management especially in terms of green house gas emission and extended rate of leachate generation also has been discussed. The difficulties in proper collection, storage and bioconversion of food waste to valuable by-products are pointed as a big hurdle in proper waste management. Finally, the wide array of value added products developed from food waste after pretreatment are also enlisted to emphasis the prospects of food waste management.

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.

Remarkably high glucoamylase production from food waste was achieved by optimizing the fermentation conditions using the response surface methodology.

Growth, substrate consumption, and product formation kinetics of Phanerochaete chrysosporium and Schizophyllum commune mixed culture under solid-state fermentation of fruit peels

Kinetic analysis of solid-state fermentation (SSF) of fruit peels with Phanerochaete chrysosporium and Schizophyllum commune mixed culture was studied in flask and 7 kg capacity reactor. Modified Monod kinetic model suggested by Haldane sufficiently described microbial growth with co-efficient of determination (R ²) reaching 0.908 at increased substrate concentration than the classical Monod model (R ² = 0.932). Leudeking-Piret model adequately described product synthesis in non-growth-dependent manner (R ² = 0.989), while substrate consumption by P. chrysosporium and S. commune fungal mixed culture was growth-dependent (R ² = 0.938). Hanes-Woolf model sufficiently represented α-amylase and cellulase enzymes synthesis (R ² = 0.911 and 0.988); α-amylase had enzyme maximum velocity (V _max) of 25.19 IU/gds/day and rate constant (K _m) of 11.55 IU/gds/day, while cellulase enzyme had V _max of 3.05 IU/gds/day and K _m of 57.47 IU/gds/day. Product yield in the reactor increased to 32.65 mg/g/day compared with 28.15 mg/g/day in shake flask. 2.5 cm media thickness was adequate for product formation within a 6 day SSF in the tray reactor.

Production of 5-hydroxymethylfurfural from starch-rich food waste catalyzed by sulfonated biochar

Sulfonated biochar derived from forestry wood waste was employed for the catalytic conversion of starch-rich food waste (e.g., bread) into 5-hydroxymethylfurfural (HMF). Chemical and physical properties of catalyst were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, and elemental analysis. The conversion of HMF was investigated via controlling the reaction parameters such as catalyst loading, temperature, and reaction time. Under the optimum reaction conditions the HMF yield of 30.4 Cmol% (i.e., 22 wt% of bread waste) was achieved in the mixture of dimethylsulfoxide (DMSO)/deionized-water (DIW) at 180 °C in 20 min. The effectiveness of sulfonated biochar catalyst was positively correlated to the density of strong/weak Brønsted acidity (SO₃H, COOH, and OH groups) and inversely correlated to humins content on the surface. With regeneration process, sulfonated biochar catalyst displayed excellent recyclability for comparable HMF yield from bread waste over five cycles.

Study on optimization of process parameters for enhancing the multi-hydrolytic enzyme activity in garbage enzyme produced from preconsumer organic waste

The garbage enzymes produced from preconsumer organic waste containing multi hydrolytic enzyme activity which helps to solubilize the waste activated sludge. The continuous production of garbage enzyme and its scaling up process need a globe optimized condition. In present study the effect of fruit peel composition and sonication time on enzyme activity were investigated. Garbage enzyme produced from 6g pineapple peels: 4g citrus peels pre-treated with ultrasound for 20min shows higher hydrolytic enzymes activity. Simultaneously statistical optimization tools were used to model garbage enzyme production with higher activity of amylase, lipase and protease. The maximum activity of amylase, lipase and protease were predicted to be 56.409, 44.039, 74.990U/ml respectively at optimal conditions (pH (6), temperature (37°C), agitation (218 RPM) and fermentation duration (3days)). These optimized conditions can be successfully used for large scale production of garbage enzyme with higher hydrolytic enzyme activity.

Fermentative polyhydroxybutyrate production from a novel feedstock derived from bakery waste

In this study, Halomonas boliviensis was cultivated on bakery waste hydrolysate and seawater in batch and fed-batch cultures for polyhydroxybutyrate (PHB) production. Results demonstrated that bakery waste hydrolysate and seawater could be efficiently utilized by Halomonas boliviensis while PHB contents between 10 and 30% (w/w) were obtained. Furthermore, three methods for bakery waste hydrolysis were investigated for feedstock preparation. These include: (1) use of crude enzyme extracts from Aspergillus awamori, (2) Aspergillus awamori solid mashes, and (3) commercial glucoamylase. In the first method, the resultant free amino nitrogen (FAN) concentration in hydrolysates was 150 and 250 mg L⁻¹ after 20 hours at enzyme-to-solid ratios of 6.9 and 13.1 U g⁻¹, respectively. In both cases, the final glucose concentration was around 130–150 g L⁻¹. In the second method, the resultant FAN and glucose concentrations were 250 mg L⁻¹ and 150 g L⁻¹, respectively. In the third method, highest glucose and lowest FAN concentrations of 170–200 g L⁻¹ and 100 mg L⁻¹, respectively, were obtained in hydrolysates after only 5 hours. The present work has generated promising information contributing to the sustainable production of bioplastic using bakery waste hydrolysate.

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.