Sweet Potato Residue Research Articles

Effects of different extraction solvents on the compositions, primary structures, and anti-inflammatory activity of pectin from sweet potato processing by-products

To examine the effects of different solvents on the molecular weight, yield, chemical composition, and bioactivity of pectins, four RG-I type pectins were separately extracted from sweet potato residue (SPR) using hot water extraction (HWSP), sodium hydroxide extraction (SHSP), hydrochloric acid extraction (HASP), and chelating agents (CASP). The results showed that the four pectin samples comprised GalUA, Gal, Rha, Ara, Glc, GlcUA, Man, and Xyl components. Among these components, GalA content was the highest in all four pectins. SHSP exhibited relatively higher yield (3.16 %, w/w). Additionally, SHSP exhibited a lower molecular weight (44.49 kDa) and the largest proportion of the RG-I region (75.42 %) compared with other extraction methods. On the contrary, HASP showed relatively lower yield (2.14 %, w/w), and its corresponding prepared pectin had relatively high molecular weight (69.81 kDa) and the minimum range of RG-I region (46.87 %) compared with HWSP, SHSP, and CASP. The anti-inflammation effect of the four SPR pectin samples was investigated using in vitro experiments. Results showed that all of SPR pectin significantly inhibited the levels of IL-1β, IL-6, and TNF-α in lipopolysaccharide (LPS)-treated iBMDM macrophage cells. The preliminary structure-activity relationship between pectin structure and anti-inflammatory activity was also analyzed. SPR pectin can be developed as a potential bioactive ingredient for applications in the food and medicine industries.

Optimization of Consolidated Bioprocessing Fermentation of Uncooked Sweet Potato Residue for Bioethanol Production by Using a Recombinant Amylolytic Saccharomyces cerevisiae Strain via the Orthogonal Experimental Design Method

Optimization of Consolidated Bioprocessing Fermentation of Uncooked Sweet Potato Residue for Bioethanol Production by Using a Recombinant Amylolytic Saccharomyces cerevisiae Strain via the Orthogonal Experimental Design Method

Construction of an amylolytic Saccharomyces cerevisiae strain with high copies of α-amylase and glucoamylase genes integration for bioethanol production from sweet potato residue.

Sweet potato residue (SPR) is the by-product of starch extraction from fresh sweet potatoes and is rich in carbohydrates, making it a suitable substrate for bioethanol production. An amylolytic industrial yeast strain with co-expressing α-amylase and glucoamylase genes would combine enzyme production, SPR hydrolysis, and glucose fermentation into a one-step process. This consolidated bioprocessing (CBP) shows great application potential in the economic production of bioethanol. In this study, a convenient heterologous gene integration method was developed. Eight copies of a Talaromyces emersonii α-amylase expression cassette and eight copies of a Saccharomycopsis fibuligera glucoamylase expression cassette were integrated into the genome of industrial diploid Saccharomyces cerevisiae strain 1974. The resulting recombinant strains exhibited clear transparent zones in the iodine starch plates, and SDS-PAGE analysis indicated that α-amylase and glucoamylase were secreted into the culture medium. Enzymatic activity analysis demonstrated that the optimal temperature for α-amylase and glucoamylase was 60-70°C, and the pH optima for α-amylase and glucoamylase was 4.0 and 5.0, respectively. Initially, soluble corn starch with a concentration of 100 g/L was initially used to evaluate the ethanol production capability of recombinant amylolytic S. cerevisiae strains. After 7 days of CBP fermentation, the α-amylase-expressing strain 1974-temA and the glucoamylase-expressing strain 1974-GA produced 33.03 and 28.37 g/L ethanol, respectively. However, the 1974-GA-temA strain, which expressed α-amylase and glucoamylase, produced 42.22 g/L ethanol, corresponding to 70.59% of the theoretical yield. Subsequently, fermentation was conducted using the amylolytic strain 1974-GA-temA without the addition of exogenous α-amylase and glucoamylase, which resulted in the production of 32.15 g/L ethanol with an ethanol yield of 0.30 g/g. The addition of 20% glucoamylase (60 U/g SPR) increased ethanol concentration to 50.55 g/L, corresponding to a theoretical yield of 93.23%, which was comparable to the ethanol production observed with the addition of 100% α-amylase and glucoamylase. The recombinant amylolytic strains constructed in this study will facilitate the advancement of CBP fermentation of SPR for the production of bioethanol.

Extraction and Structural Analysis of Sweet Potato Pectin and Characterization of Its Gel.

Pectin is widely used in the food and pharmaceutical industries. However, data on sweet potato pectin extraction and structural property analyses are lacking. Here, for the high-value utilization of agricultural processing waste, sweet potato residue, a byproduct of sweet potato starch processing, was used as raw material. Ammonium oxalate, trisodium citrate, disodium hydrogen phosphate, hydrochloric acid and citric acid were used as extractants for the pectin constituents, among which ammonium oxalate had a high extraction rate of sweet potato pectin, low ash content and high molecular weight. Structural and gelation analyses were conducted on ammonium oxalate-extracted purified sweet potato pectin (AMOP). Analyses showed that AMOP is a rhamnogalacturonan-I-type pectin, with a molecular weight of 192.5 kg/mol. Chemical titration and infrared spectroscopy analysis confirmed that AMOP is a low-ester pectin, and scanning electron and atomic force microscopy demonstrated its linear molecular structure. Gelation studies have revealed that Ca2+ is the key factor for gel formation, and that sucrose significantly enhanced gel hardness. The highest AMOP gel hardness was observed at pH 4, with a Ca2+ concentration of 30 mg/g, pectin concentration of 2%, and sucrose concentration of 40%, reaching 128.87 g. These results provide a foundation for sweet potato pectin production and applications.

Effects of fermented sweet potato residue on nutrient digestibility, meat quality, and intestinal microbes in broilers

This study aimed to investigate the effects of different proportions of dietary fermented sweet potato residue (FSPR) supplementation as a substitute for corn on the nutrient digestibility, meat quality, and intestinal microbes of yellow-feathered broilers. Experiment 1 (force-feeding) evaluated the nutrient composition and digestibility of mixtures with different proportions of sweet potato residue (70%, 80%, 90%, and 100%) before and after fermentation. In Experiment 2 (metabolic growth), a total of 420 one-day-old yellow-feathered broilers were randomly allocated to 4 groups and fed corn-soybean meal-based diets with 0, 5%, 8%, and 10% FSPR as a substitute for corn. The force-feeding and metabolic growth experiments were performed for 9 and 70 d, respectively. The treatment of 70% sweet potato residue (after fermentation) had the highest levels of crude protein, ether extract, and crude fiber and improved the digestibility of crude protein and amino acids (P < 0.05). Although dietary FSPR supplementation at different levels had no significant effect on growth performance and intestinal morphology, it improved slaughter rate, half-chamber rate, full clearance rate, and meat color, as well as reduced cooking loss in the breast and thigh muscles (P < 0.05). Dietary supplementation with 8% and 10% FSPR increased the serum immunoglobulin M and immunoglobulin G levels in broilers (P < 0.05). Furthermore, 10% FSPR increased the Shannon index and Ruminococcaceae_UCG-014, Ruminococcaceae_UCG-010 and Romboutsia abundances and decreased Sutterella and Megamonas abundances (P < 0.05). Spearman's correlation analysis showed that meat color was positively correlated with Ruminococcaceae_UCG-014 (P < 0.05) and negatively correlated with Megamonas (P < 0.05). Collectively, 70% sweet potato residue (after fermentation) had the best nutritional value and nutrient digestibility. Dietary supplementation with 8% to 10% FSPR as a substitute for corn can improve the slaughter performance, meat quality, and intestinal microbe profiles of broilers. Our findings suggest that FSPR has the potential to be used as a substitute for corn-soybean meals to improve the meat quality and intestinal health of broilers.

Interpretation of the adsorption process of toxic Cd2+ removal by modified sweet potato residue.

Cadmium (Cd) is a common and toxic non-essential heavy metal that must be effectively treated to reduce its threat to the environment and public health. Adsorption with an adsorbent, such as agricultural waste, is widely used to remove heavy metals from wastewater. Sweet potato, the sixth most abundant food crop worldwide, produces a large amount of waste during postharvest processing that could be used as an economic adsorbent. In this study, the feasibility of using sweet potato residue (SPR) as an adsorbent for Cd2+ adsorption was assessed. To enhance the removal rate, SPR was modified with NaOH, and the effects of the modification and adsorption conditions on the removal of Cd2+ from wastewater were investigated. The results showed that modified sweet potato residue (MSPR) could be adapted to various pH and temperatures of simulated wastewater, implying its potential for multi-faceted application. Under optimized conditions, the removal of Cd2+ by MSPR was up to 98.94% with a maximum adsorption capacity of 19.81 mg g-1. Further investigation showed that the MSPR exhibited rich functional groups, a loose surface, and a mesoporous structure, resulting in advantageous characteristics for the adsorption of Cd2+. In addition, the MSPR adsorbed Cd2+ by complexation, ion exchange, and precipitation during a monolayer chemisorption adsorption process. This work demonstrates a sustainable and environment friendly strategy for Cd2+ removal from wastewater and a simple approach for the preparation of MSPR and also revealed the adsorption mechanism of Cd2+ by MSPR, thus providing a suitable adsorbent and strategy for the removal of other heavy metals.

Impact of Ganoderma lucidum fermentation on the nutritional composition, structural characterization, metabolites, and antioxidant activity of Soybean, sweet potato and Zanthoxylum pericarpium residues

One of the major issues in the food sector is the lack of resource utilization and the contamination of the environment caused by by-products. This study aimed to investigate the effects of Ganoderma lucidum (GL) fermentation on the nutritional components, structural characterization, metabolites, and antioxidant activity of soybean residue (SR), sweet potato residue (SPR), and zanthoxylum pericarpium residue (ZPR). The results showed that the nutrient contents of SR, SPR and ZPR increased. The active substances, amino acids (umami, aromatic and basic), metabolites and antioxidant activity (DPPH, ABTS, FRAP) (SR and SPR increased by 11.43, 32.64, 40.19 μmol Trolox/100 g and 19.29, 17.7, 32.35 μmol Trolox/100 g, respectively) of SR and SPR were increased. However, the results of ZPR showed a decrease in the content of bioactive substances, amino acids, and antioxidant activity. The results show that using GL fermentation can provide novel ideas and theoretical basis for improving SR and SPR to obtain new raw materials for antioxidant products.

Soil carbon mineralization, enzyme activities, and crop residue decomposition under varying soil moisture regimes

AbstractIn the Lower Mississippi River Basin, farmlands are flooded in late fall and winter by impeding drainage to provide a habitat for migratory birds stopover. A laboratory incubation study was conducted to study the influence of temporary wetting of these soils on carbon (C) and nitrogen (N) mineralization from residue decomposition. Surface soils (0–15 cm) were collected from fields with clay and silty clay loam soils. Both soils were incubated with five crop residues—corn (Zea mays), soybean (Glycine max), cotton (Gossypium hirsutum), sorghum (Sorghum bicolor), and sweet potato (Ipomea batatus)—at 50% and 100% water holding capacity (WHC). Soil carbon dioxide (CO2) efflux was measured during 74 days of incubation. Soil moisture had the largest effect on soil CO2 efflux and most of the enzyme activities followed by residue and soil type. Cumulative soil CO2 efflux was reduced by 46% at 100% WHC compared to 50% WHC. Clay soil had higher cumulative CO2 efflux, aryl sulfatase, aryl phosphatase, and β‐N‐acetyl glucose aminidase activities than silty clay loam soil. Residue type had the largest effect on post‐incubation soil inorganic‐N, remaining biomass, and residue C and residue N. Sweet potato residue had the lowest remaining biomass, significantly lower than cotton, corn, and sorghum, but statistically similar to soybean. After incubation, residue N concentration had a positive association with cumulative CO2 efflux and a negative association with remaining residue biomass percentage. Winter flooding might limit the loss of soil C as CO2 depending on the crops grown and soil type.

Preparation and Characterization of Sweet Potato Residue based on NIPU

Preparation and Characterization of Sweet Potato Residue based on NIPU

Evaluation of physicochemical properties and in vitro starch digestion of noodles enriched with thermally assisted potassium carbonate treated sweet potato residue

In this study, we investigated the effect of thermally assisted potassium carbonate treatment sweet potato residue (TAPC-SPR) and its addition (0%, 5%, 10% and 15%) on the texture, multi-scale structure (microstructure, crystalline structure, short-range ordered structure) and in vitro starch digestibility of the noodles. The results demonstrated that the ratio of total dietary fiber (TDF) (75.62%–87.25%) and pectin (19.36%–23.36%) were increased, and the particle size distribution (175.67 μm–47.42 μm) was decreased in TAPC-SPR than sweet potato residues (SPR). This study suggested that suitable TAPC-SPR (5% and 10%) contributed to improving the texture properties of noodles, containing hardness, springiness, chewiness and adhesiveness. Sensory evaluation showed that noodles with suitable TAPC-SPR (5% and 10%) had an overall sensory acceptability relative to control. In addition, the intermolecular hydrogen bond interaction, the structure order, V-type starch complex and dense structure were observed. These structural changes limit the interaction of amylase with starch, elevate the resistant starch (RS) content, and lower the predicted glycemic index (pGI).

Characterization of ice cream analogue from orange-fleshed sweet potato

This study centered on the effects of partial replacement of cow milk powder (CMP) with cooked orange-fleshed sweet potato (OFSP) residue on the quality of ice cream analogue with a view of elucidating the possible utilization of OFSP in ice cream production using a Completely Randomized Design. Ice cream analogue mixes were formulated from CMP, OFSP and other ingredients by decreasing the quantity of CMP from 800 to 0 g while increasing the quantity of OFSP from 0 to 800 g. The mixes were whipped, packed in a plastic container, frozen quickly and then stored at -18oC. The products were evaluated for chemical, physical and sensory properties using standard methods. Data generated were subjected to Analysis of Variance, while means were separated using Duncan Multiple Range Test at p&lt;0.05. The crude protein, minerals except for iron, total soluble solids, overrun and foam stability decreased significantly, while crude fibre, β-carotene and melt rate increased significantly with an increase in OFSP residue in the product. The overall acceptability scores for samples containing 100 g OFSP and 300 g OFSP residue were not significantly different from the sample without OFSP residue (control). The results suggested the possibility of substituting OFSP residue for CMP up to 37.5% of a blend of OFSP and CMP in ice cream production.

One-step enzymatic hydrolysis of sweet potato residue after gelatinization for bioethanol production by Saccharomyces cerevisiae

One-step enzymatic hydrolysis of sweet potato residue after gelatinization for bioethanol production by Saccharomyces cerevisiae

Analysis of the nutritional properties and flavor profile of sweetpotato residue fermented with Rhizopus oligosporus

Sweetpotato residue, a by-product generated after starch extraction in the food industry, has not been effectively utilized. In this study, fermentation with Rhizopus oligosporus RT-3 was carried out to improve the nutritional properties and flavor profile of sweetpotato residue. The contents of soluble dietary fiber, protein, phenolics and flavonoids and the antioxidant activities of sweetpotato residue significantly increased during fermentation. The analysis of headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and sensory evaluation indicated that fermentation enhanced the aroma of sweetpotato residue due to the increased levels of alcohols, esters, ketones, and alkenes. Metabolite analysis further revealed that fermentation remarkably improved the nutritional composition of the sweetpotato residue. The potential metabolic pathways triggered during fermentation demonstrated that the improved nutritional composition of sweetpotato residue was attributed to the biochemical reactions driven by microbial enzymes.

The Sustainability of Sweet Potato Residues from Starch Processing By-Products: Preparation with Lacticaseibacillus rhamnosus and Pediococcus pentosaceus, Characterization, and Application.

The effects of Lacticaseibacillus rhamnosus and Pediococcus pentosaceus on the nutritional-functional composition, structure, in vitro saliva-gastrointestinal digestion, and colonic fermentation behaviors of fermented sweet potato residues (FSPR) were investigated. The FSPR was obtained under the condition of a solid-to-liquid ratio of 1/10, inoculation quantity of 1.5%, mixed bacteria ratio 1:1, fermentation time of 48 h, and fermentation temperature of 37 °C. The FSPR showed higher contents of soluble dietary fiber (15.02 g/100 g), total polyphenols content (95.74 mg/100 g), lactic acid (58.01 mg/g), acetic acid (1.66 mg/g), volatile acids (34.26%), and antioxidant activities. As exhibited by FTIR and SEM, the higher peak intensity at 1741 cm-1 and looser structure were observed in FSPR. Further, the FSPR group at colonic fermentation time of 48 h showed higher content of acetic acid (1366.88 µg/mL), propionic acid (40.98 µg/mL), and butyric acid (22.71 µg/mL), which were the metabolites produced by gut microbiota using dietary fiber. Meanwhile, the abundance of Bifidobacterium and Lacticaseibacillus in the FSPR group was also improved. These results indicated that FSPR potentially developed functional foods that contributed to colonic health.

Nitrogen Removal from the Simulated Wastewater of Ionic Rare Earth Mining Using a Biological Aerated Filter: Influence of Medium and Carbon Source

In engineering application, a two-stage biological aerated filter (BAF) has been deployed to achieve the steady nitrogen removal of the wastewater from the mining area of ionic rare earth with a low carbon to nitrogen (C/N) ratio. However, the cost-efficiency of the medium and carbon source casts a shadow over further development. In this study, the influences of four media (i.e., volcanic, zeolite, quartz, and ceramisite) and three soluble carbon sources (i.e., acetate, glucose, and methanol) on the N removal were systematically compared. Applying volcanic and quartz showed a favorable start-up performance due to the biophilic surface and dense packing, respectively. However, regardless of medium type, with [NH4+-N]0 = 50 and [NO3−-N]0 = 30 mg/L, the C/N ratio of 3 was required to meet the discharge standards of NH4+-N, TN, and COD, and acetate was confirmed applicable for all the selected medium-packed BAFs. Introduction of sweet potato residues as the solid carbon source decreased the amount of added acetate by more than 13%. The 16S rRNA high-throughput gene sequencing revealed that Sphingomonas and Nitrospira were abundant in the aerobic stages of the volcanic and zeolite-packed BAFs, respectively. Such a community integrated with the extensively distributed Thauera, Clostridium_sensu_stricto, and Proteiniclasticum in the anoxic stage accounted for the efficient N removal. Thus, deploying volcanic as the medium and acetate as the soluble carbon source was proposed. These findings will provide valuable references for the selection of medium and carbon source and, consequently, further optimize the operational performance.

Non-isocyanate polyurethane from sweet potato residual and the application in food preservation

Because of the increasingly environmental and health concerns over conventional polyurethanes that manifested by toxic isocyanates and unsustainable fossil-based polyols, there is a great interest in non-isocyanate polyurethanes (NIPUs) production from renewable biomass resources. Herein, under the concept of biorefinery, the sweet potato residue (SPR) from starch industry, rich in non-biological toxicity starch, holocellulose and vegetable protein, was considered as the raw material for the NIPUs. During the process, the crude SPR was first liquified into chain-extending homogeneous molecules that were enriched in active hydroxyl-groups, followed by undergoing epoxidation and carbonation. Then, the obtained cyclic carbonate precursor was crosslinked with amines for the final NIPUs. The as-prepared SPR-derived NIPUs exhibited attractive mechanical and thermodynamic properties. To test the applicability, the food preservation performances of the SPR-derived NIPUs was further investigated. After spray coating the NIPUs on the banana peel, the dark brown spots in the testing group were significantly reduced after half-month storage. Therefore, the SPR-derived NIPUs provides a foundation for the futural food packaging alternatives.

Study on Extraction Process Optimization, Structure Identification and Functional Activity of Polysaccharide from Sweet Potato Residue

Study on Extraction Process Optimization, Structure Identification and Functional Activity of Polysaccharide from Sweet Potato Residue

Low-cost and highly efficient production of bacterial cellulose from sweet potato residues: Optimization, characterization, and application

Bacterial cellulose (BC) is an emerging biological material with unique properties and structure, which has attracted more and more attention. In this study, Gluconacetobacter xylinus was used to convert sweet potato residues (SPR) hydrolysate to BC. SPR was directly used without pretreatment, and almost no inhibitors were generated, which was beneficial to subsequent glucan conversion and SPR-BC synthesis. SPR-BC production was 11.35 g/L under the optimized condition. The comprehensive structural characterization and mechanical analysis demonstrated that the crystallinity, maximum thermal degradation temperature, and tensile strength of SPR-BC were 87.39%, 263 °C, and 6.87 MPa, respectively, which were superior to those of BC produced with the synthetic medium. SPR-BC was added to rice straw pulp to enhance the bonding force between fibers and the indices of tensile, burst, and tear of rice straw paper. The indices were increased by 83.18%, 301.27%, and 169.58%, respectively. This research not only expanded the carbon source of BC synthesis, reduced BC production cost, but also improved the quality of rice straw paper.

Nutritional composition, antioxidant activity, volatile compounds, and stability properties of sweet potato residues fermented with selected lactic acid bacteria and bifidobacteria

The effects of four kinds of lactic acid bacteria (LAB) and one bifidobacteria on nutritional composition, antioxidant activity, volatile compounds and stability properties of fermented sweet potato residues (SPR) were investigated. The soluble dietary fiber (12.92–16.63 g/100 g DW), total polyphenols content (90.51–97.35 mg/100 g DW), organic acids, and stability of SPR were increased after fermentation. The DPPH radical scavenging capacity (39.49–62.04 mg AAE/100 g DW) and ferric reducing antioxidant power (47.14–71.87 mg TE/100 g DW) were also increased, of which SPR fermented with Lacticaseibacillus rhamnosus CICC 23119 exhibited the highest values. Meanwhile, the anti-nutritional compound (oxalic acid) was decreased from 0.46 to 0.08–0.30 mg/g DW. Also, the fermented SPR exhibited different flavors compared with SPR, due to the production of acids especially antiseptic hexanoic acid and sorbic acid. Therefore, these results can provide a theoretical basis for the high-value utilization of SPR.

Waste-to-energy: biobutanol production from cellulosic residue of sweet potato by Clostridia acetobutylicum

Biobutanol has been emerging as a renewable replacement to overcome fossil fuel limit due to its attractive qualities. The waste resources utilization is an economically feasible and eco-friendly way to produce biobutanol. In this work, the potential of butanol fermentation with sweet potato residue (SPR) obtained from ethanol fermentation was evaluated. To assist sugar release for butanol production by Clostridia acetobutylicum, a pretreatment approach with dilute sulfuric acid was established via response surface methodology. The maximum butanol concentration of 3.77 g/L was obtained at the optimal conditions of pretreatment at 1% (v/v) dilute sulfuric acid, and 115℃ for 30 min. Detoxifying the hydrolysate with XAD-4 resin significantly enhanced butanol fermentation performance, while adding nutritional supplements had no significant influence. The stability of the fermentation process was verified by the 2 L-scale of fermentation, resulting in 7.96 g/L of butanol, 13.42 g/L h of Acetone-Butanol-Ethanol (ABE), and 0.34 g/g of ABE yield, respectively. This study demonstrates a bio-refinery strategy of conversion from waste biomass to energy, confirms the feasibility of utilizing the cost saving SPR as feedstock to produce butanol through fermentation, and provides a novel approach for minimization of environmental pollution.