Production of pectinases by solid-state fermentation of a mixture of citrus waste and sugarcane bagasse in a pilot-scale packed-bed bioreactor

Exploring biorefinery alternatives for biowaste valorization: a techno-economic assessment of enzymatic hydrolysis coupled with anaerobic digestion or solid-state fermentation for high-value bioproducts

Enzymatic hydrolysis of organic waste is gaining relevance as a complementary technology to conventional biological treatments. Moreover, biorefineries are emerging as a sustainable scenario to integrate waste valorization and high-value bioproducts production. However, their application on municipal solid waste is still limited. This study systematically evaluates the techno-economic feasibility of the conversion of the organic fraction of municipal solid waste (OFMSW) into high-value bioproducts through enzymatic hydrolysis. Two key variables are examined: (a) the source of the enzymes: commercial or on-site produced using OFMSW, and (b) the treatment of the solid hydrolyzate fraction: solid-state fermentation (SSF) for the production of biopesticides or anaerobic digestion for the production of energy. As a result, four different biorefinery scenarios are generated and compared in terms of profitability. Results showed that the most profitable scenario was to produce enzymes on-site and valorize the solid fraction via SSF, with an internal rate of return of 13%. This scenario led to higher profit margins (74%) and a reduced payback time (6 years), in contrast with commercial enzymes that led to an unprofitable biorefinery. Also, the simultaneous production of higher-value bioproducts and energy reduced the economic dependence of OFMSW treatment on policy instruments while remaining energetically self-sufficient. The profitability of the biorefinery scenarios evaluated was heavily dependent on the enzyme price and the efficiency of the anaerobic digestion process, highlighting the importance of cost-efficient enzyme production alternatives and high-quality OFMSW. This paper contributes to understanding the potential role of enzymes in future OFMSW biorefineries and offers economical insights on different configurations.

Thermoalkalophilic polygalacturonase from a novel Glutamicibacter sp.: Bioprospecting, strain improvement, statistical optimization and applications

The current research discusses a multidimensional bioprocess development, that includes bioprospecting, strain improvement, media optimisation, and applications of the extracted enzyme. A potent alkalophilic polygalacturonase (PG) producing bacterial strain was isolated and identified as a novel Glutamicibacter sp. Furthermore, strain improvement by UV and chemical mutagenesis not only improved the enzyme (PGmut) production but also enhanced its temperature optima from 37 °C to 50 °C. The use of solid substrate fermentation, followed bystatistical optimisation through PB and RSM, substantially increasedPGmut production. A 10-fold increase in enzyme production (632 U/gm) was observed when sugarcane bagasse with a pH of 10.5, 66.8 % moisture, and an inoculum size of 10.15 % was used. The model's accuracy was supported by p-value (p < 0.0001), and an R2 of 0.9940. A pilot-scale experiment, demonstrated ≈ 62,229 U/100 gm PG activity. Additionally, the enzyme's efficacy in demucilization of coffee beans, and bioscouring of jute fibre indicated that it is a valuable biocatalyst.

A Critical Evaluation of Recent Studies on Packed-Bed Bioreactors for Solid-State Fermentation

Packed-bed bioreactors are often used for aerobic solid-state fermentation, since the forced aeration supplies O2 and removes metabolic heat from the bed. Motivated by the potential for applications in biorefineries, we review studies conducted on packed-bed bioreactors over the last decade, evaluating the insights these studies provide into how large-scale packed beds should be designed and operated. Many studies have used low superficial air velocities and suffer from preferential airflow, such that parts of the bed are not properly aerated. Moreover, some studies have proposed ineffective strategies, such as reversing the direction of the airflow or introducing air through perforated pipes within the bed. Additionally, many studies have used narrow water-jacketed packed-bed bioreactors, but these bioreactors do not reflect heat removal in wide large-scale packed beds, in which heat removal through the side walls makes a minor contribution. Finally, we conclude that, although some attention has been given to characterizing the porosities, water sorption isotherms and volumetric heat and mass transfer coefficients of substrate beds, this work needs to be extended to cover a wider range of solid substrates, and work needs to be done to characterize how these bed properties change due to microbial growth.

Potential and Restrictions of Food-Waste Valorization through Fermentation Processes

Food losses (FL) and waste (FW) occur throughout the food supply chain. These residues are disposed of on landfills producing environmental issues due to pollutants released into the air, water, and soil. Several research efforts have focused on upgrading FL and FW in a portfolio of added-value products and energy vectors. Among the most relevant research advances, biotechnological upgrading of these residues via fermentation has been demonstrated to be a potential valorization alternative. Despite the multiple investigations performed on the conversion of FL and FW, a lack of comprehensive and systematic literature reviews evaluating the potential of fermentative processes to upgrade different food residues has been identified. Therefore, this article reviews the use of FL and FW in fermentative processes considering the composition, operating conditions, platforms, fermentation product application, and restrictions. This review provides the framework of food residue fermentation based on reported applications, experimental, and theoretical data. Moreover, this review provides future research ideas based on the analyzed information. Thus, potential applications and restrictions of the FL and FW used for fermentative processes are highlighted. In the end, food residues fermentation must be considered a mandatory step toward waste minimization, a circular economy, and the development of more sustainable production and consumption patterns.

Bioprocessing of Agro-Industrial Waste for Maximization of Pectinase Production by a Novel Native Strain Aspergillus cervinus ARS2 Using Statistical Approach

The demand for microbial pectinase has increased due to its vast applications in different industries. The current study dealt with the synthesis of pectinase by a novel native strain Aspergillus cervinus ARS2 using agro-industrial waste. Comparative studies conducted on pectinase production by submerged fermentation (SmF) and solid-state fermentation (SSF) showed that pectinase activity was more increased in SSF (44.51 ± 1.33 IU/mL) than in SmF (40.60 ± 1.15 IU/mL) when using orange peel as a substrate. Using SSF, one-factor-at-a-time (OFAT) studies were conducted, considering different process variables such as inoculum size, initial pH, incubation time, moisture content, incubation temperature, and substrate particle size, all of which affected the pectinase activity. OFAT results showed the highest pectinase activity at an inoculum size of 106 spores/mL (43.11 ± 1.06 U/mL), an incubation time of 6 days (43.81 ± 1.21 U/mL), a moisture content of 100% (44.30 ± 1.69 U/mL), a substrate particle size of 1.7 mm (42.06 ± 1.20 U/mL), an incubation temperature of 37 ℃ (45.90 ± 1.33 U/mL), and an initial pH of 4 (43.31 ± 0.89 U/mL). The identified significant process variables were then optimized by response surface methodology (RSM)-central composite design (CCD). The results showed optimum pectinase activity of 107.14 ± 0.71 IU/mL for a substrate particle size of 2 mm, an incubation temperature of 31.5 °C, an initial pH of 4.9, and a moisture content of 107%, which was obtained from the Minitab optimizer. By using statistical optimization, the pectinase production from the isolated novel fungal strain A. cervinus ARS2 was increased 2.38-fold. Therefore, the A. cervinus ARS2 strain can be further explored for large-scale pectinase production which could meet the growing industrial demands.

The Disposition of Bioactive Compounds from Fruit Waste, Their Extraction, and Analysis Using Novel Technologies: A Review

Fruit waste contains several bioactive components such as polyphenols, polysaccharides, and numerous other phytochemicals, including pigments. Furthermore, new financial opportunities are created by using fruit ‘leftovers’ as a basis for bioactivities that may serve as new foods or food ingredients, strengthening the circular economy’s properties. From a technical standpoint, organic phenolic substances have become more appealing to industry, in addition to their application as nutritional supplements or functional meals. Several extraction methods for recovering phenolic compounds from fruit waste have already been published, most of which involve using different organic solvents. However, there is a growing demand for eco-friendly and sustainable techniques that result in phenolic-rich extracts with little ecological impact. Utilizing these new and advanced green extraction techniques will reduce the global crisis caused by fruit waste management. Using modern techniques, fruit residue is degraded to sub-zero scales, yielding bio-based commodities such as bioactive elements. This review highlights the most favorable and creative methods of separating bioactive materials from fruit residue. Extraction techniques based on environmentally friendly technologies such as bioreactors, enzyme-assisted extraction, ultrasound-assisted extraction, and their combination are specifically covered.

Media Optimization by Response Surface Methodology for the Enhanced Production of Acidic Extracellular Pectinase by the Indigenously Isolated Novel Strain Aspergillus cervinus ARS2 Using Solid-State Fermentation

Pectinolytic enzymes are related enzymes that hydrolyze pectic substances. Pectinolytic enzymes are of great interest in industrial applications for softening fruits, extracting and clarifying juices, extracting olive oil, retting textile fibers, preparing gel, and isolating protoplasts. The current work presents acidic extracellular pectinase production using low-cost agro-industrial waste with the indigenously isolated novel strain Aspergillus cervinus. Two fungal isolates, ARS2 and ARS8, with maximum pectinase activity, 41.88 ± 1.57 IU/mL and 39.27 ± 1.14 IU/mL, respectively, were screened out of 27 isolates from decayed fruit peels (orange, banana, and lemon) and soil containing decomposed vegetables. The isolate ARS2, identified as Aspergillus cervinus by molecular characterization, showed the highest pectinase activity of 43.05 ± 1.38IU/mL during screening and was further used for media component screening and optimization studies. To understand their effect on pectinase activity, one-factor-at-a-time (OFAT) studies were conducted on carbon sources, nitrogen sources, and mineral salts. The OFAT results showed the highest pectinase activity for orange peel (carbon source) at 44.51 ± 1.33 IU/mL, peptone (nitrogen source) at 45.05 ± 1.04 IU/mL, and NaH2PO4 (mineral salts) at 43.21 ± 1.12 IU/mL. The most significant media components screened by the Plackett–Burman (PB) design based on the p-value, Pareto chart, and main effect plot, were orange peel (p < 0.001), peptone (p < 0.001), NaH2PO4 (p < 0.001), and KH2PO4 (p < 0.001), which were further optimized using Response Surface Methodology (RSM) and Central Composite Design (CCD). The optimization results for the media components showed a maximum pectinase activity of 105.65 ± 0.31 IU/mL for 10.63 g orange peel, 3.96 g/L peptone, 2.07 g/L KH2PO4, and 2.10 g/L NaH2PO4. Thus, it was discovered that the indigenously isolated novel strain Aspergillus cervinus ARS2 was able to successfully produce a significant amount of pectinase using agro-industrial waste. Therefore, it can be considered for the large-scale optimized production of pectinase to meet industrial demands.

Effects of a new fermented soya bean meal on growth performance, serum biochemistry profile, intestinal immune status and digestive enzyme activities in piglets

BACKGROUND

Fermented soya bean meal (FSBM) is believed to have improved nutritional qualities compared with soya bean meal (SBM) and is also cheaper than soya protein concentration (SPC) and fish meal (FM). Therefore, the present study was conducted to compare the effects of FSBM replacing SBM, SPC and FM in diets on growth performance, serum biochemistry profile, short-chain fatty acid concentrations in digesta, intestinal mucosal enzyme activities, intestinal proinflammatory cytokine concentrations and morphology in weaned piglets. One hundred and twenty 28-day-old piglets (Duroc × Landrace × Yorkshire, body weight: 6.73 ± 1.14 kg) were randomly allocated to four treatment diets (six replicate pens with five piglets per pen) containing SBM, SPC, FM or FSBM as the protein source, respectively.

RESULTS

Dietary FSBM supplementation improved average daily gain (p < 0.05), gain to feed ratio (p < 0.05), and digestibility of dry matter, gross energy, crude protein and organic matter (p < 0.05) in pigs compared with those fed SBM during 0-14 days and reduced diarrhoea rate (p < 0.05) compared with those fed SBM and FM during 0-14 days. Moreover, pigs fed FBSM had greater IgA and IgM contents and antioxidase activities than those provided SBM and SPC on day 14. In addition, the butyrate concentration in the cecum of pigs fed FSBM was greater than those fed the other diets (p < 0.05), and the trypsin activity in duodenum and jejunum of pigs provided FSBM was greater than those fed SBM (p < 0.05). Moreover, higher villus height (p < 0.05) and villus height to crypt depth ratio (p < 0.05) and lower crypt depth (p < 0.05) in the duodenum of pigs fed FSBM were observed, and pigs fed FSBM had a lower (p < 0.05) TNF-α concentration in jejunum compared with those fed SBM.

CONCLUSIONS

In conclusion, dietary FSBM supplementation to replace SBM, SPC and FM could improve piglets' growth performance, intestinal health and immune function.

Pectinases Secretion by Saccharomyces cerevisiae: Optimization in Solid-State Fermentation and Identification by a Shotgun Proteomics Approach

A sequential design strategy was applied to optimize the secretion of pectinases by a Saccharomyces cerevisiae strain, from Brazilian sugarcane liquor vat, on passion fruit residue flour (PFRF), through solid-state fermentation (SSF). A factorial design was performed to determine the influence variables and two rotational central composite designs were executed. The validated experimental result was of 7.1 U mL⁻¹ using 50% PFRF (w/w), pH 5, 30 °C for 24 h, under static SSF. Polygalacturonase, pectin methyl esterase, pectin–lyase and pectate–lyase activities were 3.5; 0.08; 3.1 and 0.8 U mL⁻¹, respectively. Shotgun proteomics analysis of the crude extract enabled the identification of two pectin–lyases, one pectate–lyase and a glucosidase. The crude enzymatic extract maintained at least 80% of its original activity at pH values and temperatures ranging from 2 to 8 and 30 to 80 °C, respectively, over 60 min incubation. Results revealed that PFRF might be a cost-effective and eco-friendly substrate to produce pectinases. Statistical optimization led to fermentation conditions wherein pectin active proteins predominated. To the extent of our knowledge, this is the first study reporting the synthesis of pectate lyase by S. cerevisiae.

Extracting Total Anthocyanin from Purple Sweet Potato Using an Effective Ultrasound-Assisted Compound Enzymatic Extraction Technology

This study aimed to develop an effective technique for extracting total anthocyanins from purple sweet potato (Mianzishu 9) (PSP9) by ultrasound-assisted compound enzymatic extraction (UAEE). Single-factor experiments, Plackett-Burman experimental design, and response surface methodology were utilized for optimizing extraction conditions, and the antioxidant activities were evaluated. Anthocyanins were also measured using an ultra-performance liquid chromatograph linked to a mass spectrometer (UPLC-MS). The maximum yield of total anthocyanins was 2.27 mg/g under the following conditions: the ethanol concentration was 78%, the material-to-liquid ratio was 1:15 g/mL, the enzyme ratio (cellulase: pectinase: papain) was 2:2:1 and its hydrolysis was at 41 °C, pH = 4.5, 1.5 h, the ultrasonication was at 48 °C and conducted twice for 20 min each time. In addition to higher yield, anthocyanins extracted from purple sweet potato by UAEE showed great ability to scavenge DPPH (IC₅₀ of 0.089 μg/mL) and hydroxyl radicals (IC₅₀ of 100.229 μg/mL). Five anthocyanins were found in the purple sweet potato extract from UAEE. Taken together, the ultrasound-assisted compound enzymatic method can rapidly and effectively extract anthocyanins with greater antioxidant capacity from purple sweet potato.

Advances in research on solid-state fermented feed and its utilization: The pioneer of private customization for intestinal microorganisms

With sustainable development of biotechnology, increasing attention has been placed on utilization of solid-state fermented feed (SFF). Solid-state fermented feed has been a candidate strategy to alleviate the contradiction between supply and demand of feed resources, ensure food hygiene safety, promoting energy conservation, and emission reduction. In production of SFF, a variety of organic acids, enzymes, vitamins, peptides, and other unknown growth factors are produced, which could affect performance of animals. Solid-state fermented feed produced by different fermentation techniques has great instability on different physiological stages of different animals, which hinders the application and standardized production of SFF. Herein, we summarize the current advances in the role of the characteristics of SFF prepared by different manufacturing technique and its research progress in animal experiments on growth performance, gastrointestinal ecology, and immune system, so as to provide references for further acquiring a relatively perfect set of SFF production and evaluation systems.

Bio Discarded from Waste to Resource

The modern linear agricultural production system allows the production of large quantities of food for an ever-growing population. However, it leads to large quantities of agricultural waste either being disposed of or treated for the purpose of reintroduction into the production chain with a new use. Various approaches in food waste management were explored to achieve social benefits and applications. The extraction of natural bioactive molecules (such as fibers and antioxidants) through innovative technologies represents a means of obtaining value-added products and an excellent measure to reduce the environmental impact. Cosmetic, pharmaceutical, and nutraceutical industries can use natural bioactive molecules as supplements and the food industry as feed and food additives. The bioactivities of phytochemicals contained in biowaste, their potential economic impact, and analytical procedures that allow their recovery are summarized in this study. Our results showed that although the recovery of bioactive molecules represents a sustainable means of achieving both waste reduction and resource utilization, further research is needed to optimize the valuable process for industrial-scale recovery.

Production of Sucrolytic Enzyme by Bacillus licheniformis by the Bioconversion of Pomelo Albedo as a Carbon Source

Recently, there has been increasing use of agro-byproducts in microbial fermentation to produce a variety of value-added products. In this study, among various kinds of agro-byproducts, pomelo albedo powder (PAP) was found to be the most effective carbon source for the production of sucrose hydrolyzing enzyme by Bacillus licheniformis TKU004. The optimal medium for sucrolytic enzyme production contained 2% PAP, 0.75% NH₄NO₃, 0.05% MgSO₄, and 0.05% NaH₂PO₄ and the optimal culture conditions were pH 6.7, 35 °C, 150 rpm, and 24 h. Accordingly, the highest sucrolytic activity was 1.87 U/mL, 4.79-fold higher than that from standard conditions using sucrose as the carbon source. The purified sucrolytic enzyme (sleTKU004) is a 53 kDa monomeric protein and belongs to the glycoside hydrolase family 68. The optimum temperature and pH of sleTKU004 were 50 °C, and pH = 6, respectively. SleTKU004 could hydrolyze sucrose, raffinose, and stachyose by attacking the glycoside linkage between glucose and fructose molecules of the sucrose unit. The K_m and V_max of sleTKU004 were 1.16 M and 5.99 µmol/min, respectively. Finally, sleTKU004 showed strong sucrose tolerance and presented the highest hydrolytic activity at the sucrose concentration of 1.2 M–1.5 M.

Sophorolipids Production from Oil Cake by Solid-State Fermentation. Inventory for Economic and Environmental Assessment

Biosurfactants are being proposed as a substitute for surfactants in the framework of a circular economy strategy. Sophorolipids (SL) are a type of biosurfactant produced by yeast that can be produced through submerged or solid-state fermentation (SSF) processes. Even though sophorolipids are being produced at full scale, through submerged fermentations, environmental and technoeconomic information regarding its production through SSF is unavailable. An inventory of data necessary to perform preliminary economic and environmental assessments is presented in this study. Data was obtained from three SSF processes at 22-L reactor volume and from two SSF processes at 100-L reactor volume, using winterization oil cake and molasses as substrates, wheat straw as support material, and Starmerella bombicola as SL producing yeast. The effect of increasing the operation scale was assessed. Besides presenting parameters such as inoculum production, initial mass of substrates, and airflow requirements; process emissions (NH3, Volatile Organic Compounds, N2O, SH2 and CH4) and the biogas potential of the spent fermentation solids were also presented.

Improving enzyme production by solid-state cultivation in packed-bed bioreactors by changing bed porosity and airflow distribution

Enzymes production by solid-state cultivation in packed-bed bioreactor needs to be improved by mathematical modeling and also by experimentation. In this work, a mixture of sugarcane bagasse and wheat bran was used for the growth of the fungus Myceliophthora thermophila I-1D3b, able to secrete endoglucanase and xylanase, enzymes of interest in the second-generation ethanol production. Bench and pilot-scale bioreactors were used for the experiments, while critical parameters as bed porosity and airflow distribution were evaluated. Results showed enzymes with higher activities for the most porous medium, even though the less substrate amount to be cultivated. For the pilot-scale bioreactor, only the most porous medium was evaluated using different airflow distribution techniques. Using an inner tube for air supply resulted in more homogeneous enzyme production, with higher activities. The results here presented will be helpful for the scale-up of this class of bioreactor into industrial apparatuses.

Extracellular L-asparaginase production in solid-state fermentation by using sugarcane bagasse as support material

L-asparaginase is an important enzyme used in the pharmaceutical and food industry, which can be produced by different microorganisms using low cost feedstocks. In this work, sugarcane bagasse (SCB) was used as support for enzyme production in solid-state fermentation (SSF) by A. terreus. Initially, the influence of the variables carbon and nitrogen sources on the enzyme production was studied following an experimental design carried out in Erlenmeyer flasks. Statistical analysis indicated the use of 0.54% of starch, 0% of maltose, 0.44% of asparagine, and 1.14% of glutamine in the medium, resulting in enzyme activity per volume of produced extract of 120.723 U/L. Then, these conditions were applied in a horizontal column reactor filled with SCB, producing 105.3 U/L of enzyme activity. Therefore, the potential of extracellular L-asparaginase enzyme production in the column reactor using sugarcane bagasse as support was demonstrated and it represents a system that can favor large scale production.

Design and Operation of a Pilot-Scale Packed-Bed Bioreactor for the Production of Enzymes by Solid-State Fermentation

In this review, we describe our experience in building a pilot-scale packed-bed solid-state fermentation (SSF) bioreactor, with provision for intermittent mixing, and the use of this bioreactor to produce pectinases and lipases by filamentous fungi. We show that, at pilot scale, special attention must be given to several aspects that are not usually problematic when one works with laboratory-scale SSF bioreactors. For example, it can be a challenge to produce large amounts of inoculum if the fungus does not sporulate well. Likewise, at larger scales, the air preparation system needs as much attention as the bioreactor itself. Sampling can also be problematic if one wishes to avoid disrupting the bed structure. In the fermentations carried out in the pilot bioreactor, when the substrate bed contained predominantly wheat bran, the bed shrank away from the walls, providing preferential flow paths for the air and necessitating agitation of the bed. These problems were avoided by using beds with approximately 50% of sugarcane bagasse. We also show how a mathematical model that describes heat and water transfer in the bed can be a useful tool in developing appropriate control schemes. Graphical Abstract.

It Is the Mix that Matters: Substrate-Specific Enzyme Production from Filamentous Fungi and Bacteria Through Solid-State Fermentation

Fungi have a diverse spectrum of extracellular enzymes. In nature, extracellular enzymes primarily serve to procure nutrients for the survival and growth of the fungi. Complex polymers such as lignocellulose and starch as well as proteins and fats are broken down into their basic building blocks by extracellular enzymes such as amylases, proteases, lipases, xylanases, laccases, and many more.The abilities of these enzymes are made use of in diverse areas of industry, including food technology, textiles, and pharmaceuticals, and they have become indispensable for today's technology. Enzyme production is usually carried out using submerged fermentation (SmF). However, as part of the search for more sustainable uses of raw materials, solid-state fermentation (SSF) has become the focus of research.The rate of enzyme formation depends on different factors, for example, microorganism, temperature, or oxygen supply. However, one of the most important factors in enzyme production is the choice of substrate, which varies depending on the desired target enzyme. Substrates with proven effectiveness include wheat bran and straw, but unusual agricultural residues such as forage cactus pears and orange peels have surprisingly positive effects on enzyme formation as well.This review gives an overview of various technically relevant enzymes produced by filamentous fungi and suitable substrates for the production of the enzymes by SSF. Graphical Abstract.

A Review on Bioconversion of Agro-Industrial Wastes to Industrially Important Enzymes

Agro-industrial waste is highly nutritious in nature and facilitates microbial growth. Most agricultural wastes are lignocellulosic in nature; a large fraction of it is composed of carbohydrates. Agricultural residues can thus be used for the production of various value-added products, such as industrially important enzymes. Agro-industrial wastes, such as sugar cane bagasse, corn cob and rice bran, have been widely investigated via different fermentation strategies for the production of enzymes. Solid-state fermentation holds much potential compared with submerged fermentation methods for the utilization of agro-based wastes for enzyme production. This is because the physical⁻chemical nature of many lignocellulosic substrates naturally lends itself to solid phase culture, and thereby represents a means to reap the acknowledged potential of this fermentation method. Recent studies have shown that pretreatment technologies can greatly enhance enzyme yields by several fold. This article gives an overview of how agricultural waste can be productively harnessed as a raw material for fermentation. Furthermore, a detailed analysis of studies conducted in the production of different commercially important enzymes using lignocellulosic food waste has been provided.

Fermentation: A Boon for Production of Bioactive Compounds by Processing of Food Industries Wastes (By-Products)

A large number of by-products or wastes are produced worldwide through various food industries. These wastes cause a serious disposable problem with the environment. So, now a day's different approaches are used for alternative use of these wastes because these by-products are an excellent source of various bioactive components such as polyphenols, flavonoids, caffeine, carotenoids, creatine, and polysaccharides etc. which are beneficial for human health. Furthermore, the composition of these wastes depends on the source or type of waste. Approximately half of the waste is lignocellulosic in nature produced from food processing industries. The dissimilar types of waste produced by food industries can be fortified by various processes. Fermentation is one of the oldest approaches and there are three types of fermentation processes that are carried out such as solid state, submerged and liquid fermentation used for product transformation into value added products through microorganisms. Selections of the fermentation process are product specific. Moreover, various studies were performed to obtain or fortified different bioactive compounds that are present in food industries by-products or wastes. Therefore, the current review article discussed various sources, composition and nutritive value (especially bioactive compounds) of these wastes and their management or augmentation of value-added products through fermentation.

Pectinolytic enzymes-solid state fermentation, assay methods and applications in fruit juice industries: a review

A plethora of solid substrates, cultivation conditions and enzyme assay methods have been used for efficient production and estimation of polygalacturonase and pectin methylesterase enzymes. Recent developments in industrial biotechnology offer several opportunities for the utilization of low cost agro-industrial waste in Solid State Fermentation (SSF) for the pectinolytic enzyme production using fungi. Fruit waste mainly citrus fruit waste alone and along with other agro-industrial waste has been explored in SSF for enzyme production. Agro-industrial waste, due to the economic advantage of low procuring cost has been employed in SSF bioreactors for pectinolytic enzyme production. Acidic pectinases produced by fungi are utilized especially in food industries for clarification of fruit juices. This review focuses on the recent developments in SSF processes utilizing agro-industrial residues for polygalacturonase and pectin methylesterase production, their various assay methods and applications in fruit juice industries.

Bioreactors in solid state fermentation technology: Design, applications and engineering aspects

In recent years, substantial credibility in employing Solid-State Fermentation (SSF) technique has been witnessed owing to its numerous advantages over submerged fermentation (SmF). In spite of enormous advantages, true potential of SSF technology has not been fully realized at industrial scale. The lack of rational and scalable bioreactor designs backed by mathematical models and automated control system that could successfully address heterogeneity with respect to heat and mass, and also operate aseptically, remains the prime reason for it. As a result, there still exists vast scope in SSF bioreactor research and development to facilitate broad spectrum of biotechnological applications. The present article reviews state-of-the-art in SSF technology with focus on bioreactors that have been employed for bioprocess applications, in particular, enzyme production. Based on the mode of operation, bioreactors are divided into four categories with emphasis on design features, effect of operating conditions on productivity, applications and limitations. Selected modeling studies developed over the years, have been revised and presented in problem specific manner in order to address the limitations. Some interesting designs including few recent ones that have been proposed and/or employed at pilot and industrial levels are discussed in more detail.

Complete genome sequence of Bacillus velezensis 157 isolated from Eucommia ulmoides with pathogenic bacteria inhibiting and lignocellulolytic enzymes production by SSF

Bacillus velezensis 157 was isolated from the bark of Eucommia ulmoides, and exhibited antagonistic activity against a broad spectrum of pathogenic bacteria and fungi. Moreover, B. velezensis 157 also showed various lignocellulolytic activities including cellulase, xylanase, α-amylase, and pectinase, which had the ability of using the agro-industrial waste (soybean meal, wheat bran, sugarcane bagasse, wheat straw, rice husk, maize flour and maize straw) under solid-state fermentation and obtained several industrially valuable enzymes. Soybean meal appeared to be the most efficient substrate for the single fermentation of B. velezensis 157. Highest yield of pectinase (19.15 ± 2.66 U g-1), cellulase (46.69 ± 1.19 U g-1) and amylase (2097.18 ± 15.28 U g-1) was achieved on untreated soybean meal. Highest yield of xylanase (22.35 ± 2.24 U g-1) was obtained on untreated wheat bran. Here, we report the complete genome sequence of the B. velezensis 157, composed of a circular 4,013,317 bp chromosome with 3789 coding genes and a G + C content of 46.41%, one circular 8439 bp plasmid and a G + C content of 40.32%. The genome contained a total of 8 candidate gene clusters (bacillaene, difficidin, macrolactin, butirosin, bacillibactin, bacilysin, fengycin and surfactin), and dedicates over 15.8% of the whole genome to synthesize secondary metabolite biosynthesis. In addition, the genes encoding enzymes involved in degradation of cellulose, xylan, lignin, starch, mannan, galactoside and arabinan were found in the B. velezensis 157 genome. Thus, the study of B. velezensis 157 broadened that B. velezensis can not only be used as biocontrol agents, but also has potentially a wide range of applications in lignocellulosic biomass conversion.

Cellulase and xylanase production at pilot scale by solid-state fermentation from coffee husk using specialized consortia: The consistency of the process and the microbial communities involved

Solid state fermentation is a promising technology however rising concerns related to scale up and reproducibility in a productive process. Coffee husk and a specialized inoculum were used in a 4.5L and then in 50L reactors to assess the reproducibility of a cellulase and hemicellulase production system. Fermentations were consistent in terms of cellulase production and microbial communities. The higher temperatures achieved when operating at 50L generated a shift on the microbial communities and a reduction of nearly 50% on cellulase production at pilot scale. In spite, an overall enzymatic production of 3.1±0.5FPUg^-1DM and 48±4Ug^-1DM for FPase and Xyl activities was obtained, respectively, with low deviation coefficients of 16 and 19% for FPase and Xyl production. Gaseous emissions assessment revealed an emission factor of 2.6·10^-3kg volatile organic compounds per Mg of coffee husk and negligible NH₃, CH₄ and N₂O emissions.

Production of enzymes by a newly isolated Bacillus sp. TMF-1 in solid state fermentation on agricultural by-products: The evaluation of substrate pretreatment methods

Study on potential of different agro-industrial waste residues for supporting the growth of newly isolated Bacillus sp. TMF-1 strain under solid-state fermentation (SSF) was conducted aiming to produce several industrially valuable enzymes. Since the feasibility of the initial study was confirmed, further objectives included evaluation of several pretreatments of the studied agricultural by-products (soybean meal, sunflower meal, maize bran, maize pericarp, olive oil cake and wheat bran) on the microbial productivity as means of enhancing the yields of produced proteases, α-amylases, cellulases and pectinases. Among acid/alkaline treatment, ultrasound and microwave assisted methods, chemical treatments superiorly affected most of the studied substrates. Highest yields of produced proteases (50.5IUg-1) and α-amylases (50.75IUg-1) were achieved on alkaline treated corn pericarp. Alkaline treatment also promoted the secretion of cellulases on maize bran (1.19IUg-1). Highest yield of pectinases was obtained on untreated soybean meal (64.90IUg-1).

Modelling of different enzyme productions by solid-state fermentation on several agro-industrial residues

A simple kinetic model, with only three fitting parameters, for several enzyme productions in Petri dishes by solid-state fermentation is proposed in this paper, which may be a valuable tool for simulation of this type of processes. Basically, the model is able to predict temporal fungal enzyme production by solid-state fermentation on complex substrates, maximum enzyme activity expected and time at which these maxima are reached. In this work, several fermentations in solid state were performed in Petri dishes, using four filamentous fungi grown on different agro-industrial residues, measuring xylanase, exo-polygalacturonase, cellulose and laccase activities over time. Regression coefficients after fitting experimental data to the proposed model turned out to be quite high in all cases. In fact, these results are very interesting considering, on the one hand, the simplicity of the model and, on the other hand, that enzyme activities correspond to different enzymes, produced by different fungi on different substrates.