Utilization of orange peel, a food industrial waste, in the production of exo-polygalacturonase by pellet forming Aspergillus sojae

Exploitation of microbial activities at low pH to enhance planetary health

Awareness is growing that human health cannot be considered in isolation but is inextricably woven with the health of the environment in which we live. It is, however, under-recognized that the sustainability of human activities strongly relies on preserving the equilibrium of the microbial communities living in/on/around us. Microbial metabolic activities are instrumental for production, functionalization, processing, and preservation of food. For circular economy, microbial metabolism would be exploited to produce building blocks for the chemical industry, to achieve effective crop protection, agri-food waste revalorization, or biofuel production, as well as in bioremediation and bioaugmentation of contaminated areas. Low pH is undoubtedly a key physical-chemical parameter that needs to be considered for exploiting the powerful microbial metabolic arsenal. Deviation from optimal pH conditions has profound effects on shaping the microbial communities responsible for carrying out essential processes. Furthermore, novel strategies to combat contaminations and infections by pathogens rely on microbial-derived acidic molecules that suppress/inhibit their growth. Herein, we present the state-of-the-art of the knowledge on the impact of acidic pH in many applied areas and how this knowledge can guide us to use the immense arsenal of microbial metabolic activities for their more impactful exploitation in a Planetary Health perspective.

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.

Characterization of Orange Peel Waste and Valorization to Obtain Reducing Sugars

Annually, millions of tons of foods are generated with the purpose to feed the growing world population. One particular eatable is orange, the production of which in 2018 was 75.54 Mt. One way to valorize the orange residue is to produce bioethanol by fermenting the reducing sugars generated from orange peel. Hence, the objective of the present work was to determine the experimental conditions to obtain the maximum yield of reducing sugars from orange peel using a diluted acid hydrolysis process. A proximate and chemical analysis of the orange peel were conducted. For the hydrolysis, two factorial designs were prepared to measure the glucose and fructose concentration with the 3,5-DNS acid method and UV-Visible spectroscopy. The factors were acid concentration, temperature and hydrolysis time. After the hydrolysis, the orange peel samples were subjected to an elemental SEM-EDS analysis. The results for the orange peel were 73.530% of moisture, 99.261% of volatiles, 0.052% of ash, 0.687% of fixed carbon, 19.801% of lignin, 69.096% of cellulose and 9.015% of hemicellulose. The highest concentration of glucose and fructose were 24.585 and 9.709 g/L, respectively. The results highlight that sugar production is increased by decreasing the acid concentration.

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.

Semi-continuous production of high-activity pectinases by immobilized Rhizopus oryzae using tobacco wastewater as substrate and their utilization in the hydrolysis of pectin-containing lignocellulosic biomass at high solid content

In this study, highly reactive endo- and exo-polygalacturonases (PGs) were produced from the tobacco industry wastewater using immobilized Rhizopus oryzae. Compared with free cells, immobilized cells increased enzyme activity 2.8-fold and reduced production time to 24h by shake-flask production. Moreover, the immobilized cells enabled the semi-continuous production of enzymes through repeated-batch mode for seven consecutive cycles in a scale-up bioreactor. During the first five cycles, the average endo-PG and exo-PG activities reached 307.5 and 242.6U/ml, respectively. The addition of crude enzyme for the hydrolysis of pectin-containing lignocellulosic biomass under high-gravity conditions increased glucose release 4.2-fold (115.4 vs. 29.0g/L), compared with hydrolysis using cellulase alone. This process achieves the efficient production of pectin-degrading enzymes, provides a cost-effective method for tobacco wastewater treatment, and offers the possibility to obtain fermentable sugars with high-titer from pectin-containing lignocellulosic biomass, which has important potential for the commercial production of bio-fuels.

Purification and characterization of polygalacturonase from Aspergillus fumigatus MTCC 2584 and elucidating its application in retting of Crotalaria juncea fiber

Polygalacturonases represents an important member of pectinases group of enzymes with diverse industrial applications and is widely distributed among fungi, bacteria, yeasts, plants and some plant parasitic nematodes. An endo-polygalacturonase from a new fungal source Aspergillus fumigatus MTCC 2584 was produced under solid-state fermentation conditions and was purified simply by acetone precipitation and gel-filtration chromatography technique. The approximate molecular weight of the purified PG was found to be 43.0 kDa as revealed by SDS-PAGE. The pH optimum of the purified enzyme was found to be 10.0 and was stable in the pH range of 7-10. The optimum temperature of purified PG was found to be 30 °C. The Km and Kcat of the purified enzyme were 2.4 mg/ml and 44 s-1, respectively, and the metal ions Cu2+ and K+ were found to enhance the enzyme activity while Ag+, Ca2+ and Hg2+ were inhibitory in nature. Based on its alkaline nature, the potential of purified PG in retting of natural fiber Crotalaria juncea was elucidated in the absence of EDTA. This is probably the first report of alkaline PG from Aspergillus fumigatus.

Production and Properties of a Thermostable, pH-Stable Exo-Polygalacturonase Using Aureobasidium pullulans Isolated from Saharan Soil of Algeria Grown on Tomato Pomace

Polygalacturonase is a valuable biocatalyst for several industrial applications. Production of polygalacturonase using the Aureobasidium pullulans stain isolated from Saharan soil of Algeria was investigated. Its capacity to produce polygalacturonase was assessed under submerged culture using tomato pomace as an abundant agro-industrial substrate. Optimization of the medium components, which enhance polygalacturonase activity of the strain Aureobasidium pullulans, was achieved with the aid of response surface methodology. The composition of the optimized medium was as follows: tomato pomace 40 g/L, lactose 1.84 g/L, CaCl₂0.09 g/L and pH 5.16. Practical validation of the optimum medium provided polygalacturonase activity of 22.05 U/mL, which was 5-fold higher than in unoptimized conditions. Batch cultivation in a 20 L bioreactor performed with the optimal nutrients and conditions resulted in a high polygalacturonase content (25.75 U/mL). The enzyme showed stability over a range of temperature (5–90 °C) with an optimum temperature of 60 °C with pH 5.0, exhibiting 100% residual activity after 1h at 60 °C. This enzyme was stable at a broad pH range (5.0–10). The enzyme proved to be an exo-polygalacturonase, releasing galacturonic acid by hydrolysis of polygalacturonic acid. Moreover, the exo-polygalacturonase was able to enhance the clarification of both apple and citrus juice. As a result, an economical polygalacturonase production process was defined and proposed using an industrial food by-product.

Characterization of novel thermostable polygalacturonases from Penicillium brasilianum and Aspergillus niger

The aim of this research was the partial characterization of polygalacturonase (PG) extracts produced by a newly isolated Penicillium brasilianum and Aspergillus niger in submerged fermentation. The partial characterization of the crude enzymatic extracts showed optimum activity at pH 5.5 and 37 °C for both extracts. The results of temperature stability showed that PG from both microorganisms were more stable at 55 °C. However, the enzyme obtained by P. brasilianum presents a half-life time (t 1/2 = 693.10 h), about one order of magnitude higher than those observed in for A. niger at 55 °C. In terms of pH stability, the PG produced by P. brasilianum presented higher stability at pH 4.0 and 5.0, while the PG from A. niger showed higher stability at pH 5.0.