Heat pretreatment improves the enzymatic hydrolysis of granular corn starch at high concentration

Starch hydrolysates, their impurities and the role of membrane-based technologies as a promising sustainable purification method at industrial scale

Starch hydrolysates are syrups obtained through the hydrolysis of starch with a defined carbohydrate composition and concentration. Annual harvest conditions and the availability of raw materials, such as corn, wheat, rice, potato, and certain plant roots, influence their quality. High-quality starch hydrolysate products serve numerous applications, including ingredients in food, textiles, paper, cosmetics, bioplastics, pharmaceuticals and construction. However, impurities such as colour molecules, characteristic flavours, salts, and proteins encountered in the solution along the starch processing steps can compromise product quality. With increasing emphasis on organic and sustainable production, starch hydrolysates must meet higher health and environmental standards. This review provides a comprehensive overview of starch hydrolysates production and purification. It explores the chemical processes leading to the formation of impurities and their impact on the final product composition and specific characteristics. Downstream processing methods for recovery, purification, and concentration are also investigated, comparing traditional techniques with emerging membrane-based technologies. Membrane technologies offer a potential solution for purifying plant-based starch hydrolysates efficiently and sustainably by enhancing purification while reducing energy consumption and waste generation. They operate at lower temperatures, avoiding phase transitions, extra heating, chemicals, and solvent exchanges. Although membrane technologies are widely used in various food industries, minimal research exist on their applications in starch hydrolysate processing, with limited experimental validation available. Addressing this gap, this review compiles established applications and discusses challenges hindering industrial adoption-including membrane fouling, the selection of appropriate membranes, the operational lifespan, and replacement costs,- while also identifying areas requiring further experimental research and development.

Pullulanase pretreatment of highly concentrated maltodextrin solution improves maltose yield during β-amylase-catalyzed saccharification

Increasing the substrate concentration can effectively reduce energy consumption and result in more economic benefits in the industrial production of maltose, but this process remarkably increases the viscosity, which has a negative effect on saccharification. To improve saccharification efficiency, pullulanase is usually employed. In the conventional process of maltose production, pullulanase is added at the same time with β-amylase or later, but this process seems inefficient when the substrate concentration is high. Herein, a novel method was introduced to enhance the maltose yield under high substrate concentration. The results indicated that the pullulanase pretreatment of highly concentrated maltodextrin solution for 2 h greatly affects the final conversion rate of β-amylase-catalyzed saccharification. The maltose yield reached 80.95 %, which is 11.8 % above the control value. Further examination confirmed that pullulanase pretreatment decreased the number of branch points of maltodextrin and resulted in a high content of oligosaccharides. These linear chains were suitable for β-amylase-catalyzed saccharification to produce maltose. This research offers a new effective and green strategy for starch sugar production.

Improving the thermal stability and branching efficiency of Pyrococcus horikoshii OT3 glycogen branching enzyme

In practical applications, the gelatinisation temperature of starch is high. Most current glycogen branching enzymes (GBEs, EC 2.4.1.18) exhibit optimum activity at moderate or low temperatures and quickly lose their activity at higher temperatures, limiting the application of GBEs in starch modification. Therefore, we used the PROSS strategy combined with PDBePISA analysis of the dimer interface to further improve the heat resistance of hyperthermophilic bacteria Pyrococcus horikoshii OT3 GBE. The results showed that the melting temperature of mutant T508K increased by 3.1 °C compared to wild-type (WT), and the optimum reaction temperature increased by 10 °C for all mutants except V140I. WT almost completely lost its activity after incubation at 95 °C for 60 h, while all of the combined mutants maintained >40 % of their residual activity. Further, the content of the α-1,6 glycosidic bond of corn starch modified by H415W and V140I/H415W was approximately 2.68-fold and 1.92-fold higher than that of unmodified corn starch and corn starch modified by WT, respectively. Additionally, the glucan chains of DP < 13 were significantly increased in mutant modified corn starch. This method has potential for improving the thermal stability of GBE, which can be applied in starch branching in the food industry.

Synthesis and commercialization of bioplastics: Organic waste as a sustainable feedstock

Substituting synthetic plastics with bioplastics, primarily due to their inherent biodegradable properties, represents a highly effective strategy to address the current global issue of plastic waste accumulation in the environment. Advances in bioplastic research have led to the development of materials with improved properties, enabling their use in a wide range of applications in major commercial sectors. Bioplastics are derived from various natural sources such as plants, animals, and microorganisms. Polyhydroxyalkanoate (PHA), a biopolymer synthesized by bacteria through microbial fermentation, exhibits physicochemical and mechanical characteristics comparable to those of synthetic plastics. In response to the growing demand for these environmentally friendly plastics, researchers are actively investigating various cleaner production methods, including modification or derivatization of existing molecules for enhanced properties and new-generation applications to expand their market share in the coming decades. By 2026, the commercial manufacturing capacity of bioplastics is projected to reach 7.6 million tonnes, with Europe currently holding a significant market share of 43.5 %. Bioplastics are predominantly utilized in the packaging industry, indicating a strong focus of their application in the sector. With the anticipated rise in bioplastic waste volume over the next few decades, it is crucial to comprehend their fate in various environments to evaluate the overall environmental impact. Ensuring their complete biodegradation involves optimizing waste management strategies and appropriate disposal within these facilities. Future research efforts should prioritize exploration of their end-of-life management and toxicity assessment of degradation products. These efforts are crucial to ensure the economic viability and environmental sustainability of bioplastics as alternatives to synthetic plastics.

Designing a Specific Pretreatment on Corn Starch to Facilitate Enzymatic Rearrangement of Glycosidic Bonds for Efficiently Reducing Starch Digestibility

Bacterial 1,4-α-glucan branching enzymes (GBEs) provide a viable strategy for glycosidic bond rearrangement in starch and regulation of its digestion rate. However, the exponential increase in paste viscosity during starch gelatinization has a detrimental effect on the catalytic action of GBEs, thereby limiting productivity and product performance. Here, we designed an enzymatic treatment on corn starch granules by the GBE from Rhodothermus obamensis STB05 (Ro-GBE) prior to the glycosidic bond rearrangement of gelatinized starch catalyzed using the GBE from Geobacillus thermoglucosidans STB02 (Gt-GBE). Specifically, a moderate amount of Ro-GBE was required for the pretreatment stage. The dual GBE modification process enabled the treatment of more concentrated starch slurry (up to 20%, w/w) and effectively reduced starch digestibility. The resulting product contained a rapidly digestible starch fraction of 66.0%, which was 11.4% lower than that observed in the single Gt-GBE-modified product. The mechanistic investigation showed that the Ro-GBE treatment promoted swelling and gelatinization of starch granules, reduced starch paste viscosity, and increased the mobility of water molecules in the starch paste. It also created a preferable substrate for Gt-GBE. These changes improved the transglycosylation efficiency of Gt-GBE. These findings provide useful guidance for designing an efficient process to regulate starch digestibility.

Enhancing the Mechanical Properties of Corn Starch Films for Sustainable Food Packaging by Optimizing Enzymatic Hydrolysis

The objective of this study was to investigate the effects of enzymatic hydrolysis using α-amylase from Bacillus amyloliquefaciens on the mechanical properties of starch-based films. The process parameters of enzymatic hydrolysis and the degree of hydrolysis (DH) were optimized using a Box-Behnken design (BBD) and response surface methodology (RSM). The mechanical properties of the resulting hydrolyzed corn starch films (tensile strain at break, tensile stress at break, and Young's modulus) were evaluated. The results showed that the optimum DH for hydrolyzed corn starch films to achieve improved mechanical properties of the film-forming solutions was achieved at a corn starch to water ratio of 1:2.8, an enzyme to substrate ratio of 357 U/g, and an incubation temperature of 48 °C. Under the optimized conditions, the hydrolyzed corn starch film had a higher water absorption index of 2.32 ± 0.112% compared to the native corn starch film (control) of 0.81 ± 0.352%. The hydrolyzed corn starch films were more transparent than the control sample, with a light transmission of 78.5 ± 0.121% per mm. Fourier-transformed infrared spectroscopy (FTIR) analysis showed that the enzymatically hydrolyzed corn starch films had a more compact and solid structure in terms of molecular bonds, and the contact angle was also higher, at 79.21 ± 0.171° for this sample. The control sample had a higher melting point than the hydrolyzed corn starch film, as indicated by the significant difference in the temperature of the first endothermic event between the two films. The atomic force microscopy (AFM) characterization of the hydrolyzed corn starch film showed intermediate surface roughness. A comparison of the data from the two samples showed that the hydrolyzed corn starch film had better mechanical properties than the control sample, with a greater change in the storage modulus over a wider temperature range and higher values for the loss modulus and tan delta, indicating that the hydrolyzed corn starch film had better energy dissipation properties, as shown by thermal analysis. The improved mechanical properties of the resulting film of hydrolyzed corn starch were attributed to the enzymatic hydrolysis process, which breaks the starch molecules into smaller units, resulting in increased chain flexibility, improved film-forming ability, and stronger intermolecular bonds.

Designing liquefaction and saccharification processes of highly concentrated starch slurry: Challenges and recent advances

Starch-based sugars are an important group of starch derivatives used in food, medicine, chemistry, and other fields. The production of starch sugars involves starch liquefaction and saccharification processes. The production cost of starch sugars can be reduced by increasing the initial concentration of starch slurry. However, the usage of the highly concentrated starch slurry is characterized by challenges such as low reaction efficiency and poor product performance during the liquefaction and saccharification processes. In this study, we endeavored to provide a reference guide for improving high-concentration starch sugar production. Thus, we reviewed the effects of substrate concentration on the starch sugar production process and summarized several potential strategies. These regulation strategies, such as physical field pretreatment, complex enzyme-assisted, and temperature control, can significantly increase the starch concentration and mitigate the challenges of using highly concentrated starch slurry. We believe that highly concentrated starch sugar production will achieve a qualitative leap in the future. This review provides theoretical guidance and highlights the importance of high concentration in starch-based sugar production. Further studies are needed to explore the fine structure and enzyme attack mode during the liquefaction and saccharification processes to regulate the production of more targeted products.

Accelerated Shelf-Life and Stability Testing of Hydrolyzed Corn Starch Films

Nonbiodegradable food packaging films are made from plastics such as polyethylene and polypropylene, which can take hundreds of years to decompose and create environmental hazards. On the other hand, biodegradable food packaging films are made from renewable materials such as corn starch or cellulose, that degrade within a few weeks or months and prove to be more sustainable and environmentally friendly. In this work, we used corn starch hydrolyzed (CSH) with α-amylase to prepare a film with biodegradable properties. The film was tested for 60 days at different accelerated temperatures and relative humidity (RH), 13 ± 2 °C and 65 ± 5% RH, 23 ± 2 °C and 45 ± 5% RH, and 33 ± 2 °C and 30 ± 5% RH, to test its durability and stability. Soil biodegradation of the CSH film was evaluated by visual appearance, microscopic observation, weight loss, scanning electron microscopy (SEM), and Fourier-transformed infrared spectroscopy (FTIR) every 6 days. The film was found to have strong hygroscopic properties and was able to last up to 10 months if it is maintained at 20 ± 5 °C and 45 ± 5% RH. After the biodegradability test for at least 30 days, the film showed a significantly higher weight loss rate and microbial activity on the surface of the film, which indicates that the film is biodegradable. The present work recommends biodegradable CSH films as an excellent environmentally friendly choice for dried foods packaging, due to their good shelf life at room temperature, which is beneficial when shipping and storing products, but these films are not suitable for foods with high moisture content.

Modeling Based Identifiability and Parametric Estimation of an Enzymatic Hydrolysis Process of Amylaceous Materials

This work presents the modeling of an enzymatic hydrolysis process of amylaceous materials considering the parameter identification problem as a basis for the construction of the model. For this, a modeling methodology is modified in order to apply the identifiability property and improve the proposed model structure. A brief theoretical explanation of the identifiability is described. This concept is based on the observability property of a nonlinear dynamic system. The used methodology is based on the phenomenological based semiphysical model (PBSM). This methodology visualizes that the structure of a dynamic model can only improve with new mass or energy balances suggested by model suppositions. Additionally, a computer algorithm is included in the methodology to validate if the model is structurally locally identifiable or know if the parameters are unidentifiable. Also, an optimization algorithm is used to obtain the numeric values of the identifiable parameters and, hence, guarantee the validity of the result. The methodology focuses on the liquefaction and saccharification stages of an enzymatic hydrolysis process. The results of the model are compared with experimental data. The comparison shows low errors of 7.96% for liquefaction and 7.35% for saccharification. These errors show a significant improvement in comparison with previous models and validate the proposed modeling methodology.

Recent advances and sustainable development of biofuels production from lignocellulosic biomass

Many countries in the world are facing the demand for non-renewable fossil fuels because of overpopulation and economic boom. To reduce environmental pollution and zero carbon emission, the conversion of biomass into biofuels has paid better attention and is considered to be an innovative approach. A diverse raw material has been utilized as feedstock for the production of biofuel, depending on the availability of biomass, cost-effectiveness, and their geographic location. Among the different raw materials, lignocellulosic biomass has fascinated many researchers around the world. The current review discovers the potential application of lignocellulosic biomass for the production of biofuels. Various pretreatment methods have been widely used to increase the hydrolysis rate and accessibility of biomass. This review highlights recent advances in pretreatment methodologies for the enhanced production of biofuels. Detailed descriptions of the mechanism of biomass processing pathway, optimization, and modeling study have been discussed.

A temperature-mediated two-step saccharification process enhances maltose yield from high-concentration maltodextrin solutions

BACKGROUND

Designing a high-concentration (50%, w/w) maltodextrin saccharification process is a green method to increase the productivity of maltose syrup.

RESULTS

In this study, a temperature-mediated two-step process using β-amylase and pullulanase was investigated as a strategy to improve the efficiency of saccharification. During the saccharification process, both pullulanase addition time and temperature adjustment greatly impacted the final maltose yield. These results indicated that an appropriate β-amylolysis in the first stage (the first 8 h) was required to facilitate saccharification process, with the maltose yield of 8.46% greater than that of the single step saccharification. Molecular structure analysis further demonstrated that a relatively low temperature (50 °C), as compared with a normal temperature (60 °C), in the first stage resulted in a greater number of chains polymerized by at least seven glucose units and a less heterogeneity system within the residual substrate. The molecular structure of the residual substrate might be beneficial for the subsequent cooperation between β-amylase and pullulanase in the following 40 h (second stage).

CONCLUSION

Over a 48 h saccharification, the temperature-mediated two-step process dramatically increased the conversion rate of maltodextrin and yielded significantly more maltose and less byproduct, as compared with a constant-temperature process. The two-step saccharification process therefore offered an efficient and green strategy for maltose syrup production in industry. © 2020 Society of Chemical Industry.

Two 1,4-α-glucan branching enzymes successively rearrange glycosidic bonds: A novel synergistic approach for reducing starch digestibility

Enzymatically rearranging α-1,4 and α-1,6 glycosidic bonds in starch is a green approach to regulating its digestibility. A two-step modification process successively catalyzed by 1,4-α-glucan branching enzymes (GBEs) from Rhodothermus obamensi STB05 (Ro-GBE) and Geobacillus thermoglucosidans STB02 (Gt-GBE) was investigated as a strategy to reduce the digestibility of corn starch. This dual GBE modification process caused a reduction of 25.8 % in rapidly digestible starch fraction in corn starch, which were more effective than single GBE-catalyzed modification with the same duration. Structural analysis indicated that the dual GBE modified product contained higher branching density, more abundant short branches, and shorter external chains than those in single GBE-modified product. These results demonstrated that a moderate Ro-GBE treatment prior to starch gelatinization caused several suitable alterations in starch molecules, which promoted the transglycosylation efficiency of the following Gt-GBE treatment. This dual GBE-catalyzed modification process offered an efficient strategy for regulating starch digestibility.

Modification methods toward the production of porous starch: a review

Starch is a complex carbohydrate formed by the repeating units of glucose structure connected by the alpha-glycosidic linkages. Starch is classified according to their derivatives such as cereals, legumes, tubers, palms, fruits, and stems. For decades, native starch has been widely utilized in various applications such as a thickener, stabilizer, binder, and coating agent. However, starches need to be modified to enhance their properties and to make them more functional in a wide range of applications. Porous starch is a modified starch product which has attracted interest of late. It consists of abundant pores that are distributed on the granule surface without compromising the integrity of its granular structure. Porous starch can be produced either by enzymatic, chemical, and physical methods or a combination thereof. The type of starch and selection of the modification method highly influence the formation of pore structure. By carefully choosing a suitable starch and modification method, the desired morphology of porous starch can be produced and applied accordingly for its intended application. Innovations and technologies related to starch modification methods have evolved over the years in terms of the structure, properties and modification effects of different starch varieties. Therefore, this article reviews recent modification methods in developing porous starch from various origins.

Valorising Agro-industrial Wastes within the Circular Bioeconomy Concept: the Case of Defatted Rice Bran with Emphasis on Bioconversion Strategies

The numerous environmental problems caused by the extensive use of fossil resources have led to the formation of the circular bioeconomy concept. Renewable resources will constitute the cornerstone of this new, sustainable model, with biomass presenting a huge potential for the production of fuels and chemicals. In this context, waste and by-product streams from the food industry will be treated not as “wastes” but as resources. Rice production generates various by-product streams which currently are highly unexploited, leading to environmental problems especially in the countries that are the main producers. The main by-product streams include the straw, the husks, and the rice bran. Among these streams, rice bran finds applications in the food industry and cosmetics, mainly due to its high oil content. The high demand for rice bran oil generates huge amounts of defatted rice bran (DRB), the main by-product of the oil extraction process. The sustainable utilisation of this by-product has been a topic of research, either as a food additive or via its bioconversion into value-added products and chemicals. This review describes all the processes involved in the efficient bioconversion of DRB into biotechnological products. The detailed description of the production process, yields and productivities, as well as strains used for the production of bioethanol, lactic acid and biobutanol, among others, are discussed.