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.

Garbage Enzyme-Mediated treatment of landfill Leachate: A sustainable approach

The study evaluates the soluble chemical oxygen demand (sCOD) removal efficiency from landfill leachate by treating it with four different garbage enzymes at two temperatures (room temperature 27 ± 3 °C and higher temperature 42 ± 3 °C). The four different garbage enzymes were prepared by fermenting fruit peels such as pineapple, banana, orange, and lemon peels and treated with landfill leachate at different mixing ratios of 5%, 10%, 15% and 20%. The results show that garbage enzymes made from orange (10%) and lemon (15%) have maximum sCOD reduction of 68.24% and 67.89%, respectively, at room temperature. The maximum solubilization was found in the pineapple and lemon garbage enzyme at 5% concentration. The samples kept at room temperature showed better solubilization and sCOD removal compared to the samples at higher temperatures. The study demonstrates that the garbage enzyme could be used to increase the bioavailability of organics in leachate.

Food waste and soybean curd residue composting by black soldier fly

This study attempted to manage the food waste and soybean curd residue generated in Taiwan's National Ilan University by black soldier fly-aided co-composting. The food waste and soybean curd residue were co-composted with rice husk as a bulking agent in 4:1 ratio and 0.42 mg BSF/g waste. The higher organic matter degradation of 31.9% was found in Container B (black soldier flies aided food waste and rice husk co-composting) with a rate constant of 0.14 d-1. In Container D (black soldier flies aided soybean curd residue and rice husk co-composting), the organic matter degradation of 29.4% was found with a rate constant of 0.29 d-1. The matured compost of 6.02 kg was obtained from 20 kg of food waste, while 5.83 kg of matured compost was generated from 20 kg of soybean curd residue. The physico-chemical parameters of the final matured compost were in the favorable range of Taiwan's compost standards. The germination index was 188.6% and 194.78% in Containers B and D, respectively. The present study will expand the application of BSF at the institutional level which prove to be a feasible solution for rapid, clean, and efficient composting of post-consumer food wastes.

Combined addition of biochar and garbage enzyme improving the humification and succession of fungal community during sewage sludge composting

The influences of combination of garbage enzyme and biochar on total organic carbon (TOC) degradation, humification and the fungal succession during sewage sludge (SS) composting were established. Results showed that the GE and BC + GE treatments significantly increased the enzyme activity of fluorescein diacetate hydrolase (FDA) and increased the TOC degradation rate by 9.8% and 21.9% relative to control. The excitation-emission matrix (EEM) combined with the percentage fluorescence response (Pi, n) also proved that the combination of BC and GE promoted fulvic acid-like and humic-like substances production, and thus increased humification. Furthermore, the combination of BC and GE effectively decreased the relative abundance of Unclassified_k_Fugni, while increased the abundance of Ascomycota and Basidiomycota compared with control. The four genera, Pseudeurotium, Talaromyces, Trichoderma, and Penicillium, were the main fungi for the humification. Comparatively, the combined of BC and GE showed the optimal performance for TOC degradation and humification during SS composting.

Comparative evaluation of biochar, pelelith, and garbage enzyme on nitrogenase and nitrogen-fixing bacteria during the composting of sewage sludge

This study investigated the effects of garbage enzyme (GE), pelelith (PL), and biochar (BC) on nitrogen (N) conservation, nitrogenase (Nase) and N-fixing bacteria during the composting of sewage sludge. Results showed that the addition of GE, PL, and BC reduced NH₃ emissions by 40.9%, 29.3%, and 67.4%, and increased the NO₃-N contents of the end compost by 161.4, 88.2, and 105.8% relative to control, respectively, thus increasing the TN content. Three additives improved Nase, cellulase, and fluorescein diacetate hydrolase (FDA) activities and the abundances of nifH gene, and the largest increase was BC, followed by PL and GE. In addition, the additives also markedly influenced the succession of N-fixing bacteria, and significantly increased the abundance of Proteobacteria during the whole process. The BC and PL additions strengthened the sensitivity of N-fixing bacteria to environmental variables, and FDA, TN, moisture content, and NO₃-N significantly affected the N-fixing bacteria at genus level.

Garbage enzymes effectively regulated the succession of enzymatic activities and the bacterial community during sewage sludge composting

This study evaluated nitrogen transformation, enzymatic activities and bacterial succession during sewage sludge composting with and without garbage enzymes (GE and CK, respectively). The results showed that GE addition significantly increased fluorescein diacetate hydrolase (FDA), cellulase, and nitrogenase activities during the composting process. GE addition reduced the cumulative NH₃ emissions by 66.5%, increased the peak NH₄-N content by 26.3% and increased the total nitrogen (TN) content of the end compost by 39.2% compared to CK. Microbiological analysis revealed that GE addition significantly increased the relative abundance of Firmicutes during the thermophilic and cooling phases relative to CK. The selected factors affected the bacterial community composition in the following order: NH₄-N > TOC > FDA > TN > C/N. Network analysis also showed that the enzymes were secreted mainly by Bacillus and norank_f_Caldilineaceae in GE, while they were secreted primarily by norank_f_Methylococcaceae in CK during the composting process.

Exploring the synergic effect of fly ash and garbage enzymes on biotransformation of organic wastes in in-vessel composting system

The aim of the present work was to study the synergic effect of fly ash (FA) and garbage enzymes (GE) on biotransformation of organic wastes in in-vessel composting system. In-vessel composting of organic waste (household + brown in vessel 1) was performed with fly ash (mixed 5% in vessel 2; 10% in vessel 3; 15% in vessel 4; and 20% in vessel 5) by addition of extra carbon source (5%) and garbage enzyme in a fixed-dose (5%) for 15 days and changes in chemical properties (C: N ratio, nitrates, sulphates, phosphates and macro-elements) were analyzed at maturity. Vessel 5 showed better results in terms of organic matter degradability and C: N ratio (13.68) of mature compost. Principal Component Analysis (PCS) also confirmed vessel 5 as the best performing among other vessels. FTIR analysis indicated a major shift in chemical structure of organic waste due to the composting action.

Treatment of urban municipal landfill leachate utilizing garbage enzyme

In the present study, an attempt has been made to extend the application of garbage enzyme (GE) (fermented mixture of jaggery, organic waste, and water in the ratio 1:3:10) from the domestic wastewater to the urban municipal landfill leachate of Ghazipur, Okhla and Bhalswa landfill sites of Delhi (India). The Leachate Pollution Index (LPI) has been found to be 27.6, 25.4 and 29.2, respectively. The competence of GE was assessed by comparing the initial and final LPIs. The GE was added to the leachate for the contact period of 7-28 days under different mix proportions of 5%, 10%, 15%, and 20%. The maximum final LPI reduction of 74.75% was observed in the Okhla landfill leachate for mixing the proportion of 20% GE after 28 days. However, the mixing ratio of 5% GE showed significant reduction of 60.61% and 55.12% in the final LPI of Ghazipur and Bhalswa landfill leachate, respectively.

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.

Identification and optimization of parameters for the semi-continuous production of garbage enzyme from pre-consumer organic waste by green RP-HPLC method

Reuse and management of organic solid waste, reduce the environmental impact on human health and increase the economic status by generating valuable products for current and novel applications. Garbage enzyme is one such product produced from fermentation of organic solid waste and it can be used as liquid fertilizer, antimicrobial agents, treatment of domestic wastewater, municipal and industrial sludge treatment, etc. The semi-continuous production of garbage enzyme in large quantity at minimal time period and at lesser cost is needed to cater for treatment of increasing quantities of industrial waste activated sludge. This necessitates a parameter for monitoring and control for the scaling up of current process on semi-continuous basis. In the present study a RP-HPLC (Reversed Phase-High Performance Liquid Chromatography) method is used for quantification of standard organic acid at optimized condition 30°C column oven temperature, pH 2.7, and 0.7 ml/min flow rate of the mobile phase (potassium dihydrogen phosphate in water) at 50mM concentration. The garbage enzyme solution collected in 15, 30, 45, 60, 75 and 90 days were used as sample to determine the concentration of organic acid. Among these, 90th day sample showed the maximum concentration of 78.14 g/l of acetic acid in garbage enzyme, whereas other organic acids concentration got decreased when compare to the 15th day sample. This result confirms that the matured garbage enzyme contains a higher concentration of acetic acid and thus it can be used as a monitoring parameter for semi-continuous production of garbage enzyme in large scale.