Transformation of rice bran into single-cell protein, extracted protein, soluble and insoluble dietary fiber, and minerals.

BACKGROUND: It is evident that, during the conversion of agricultural sidestreams into valuable substances, a complete utilization is necessary for economic reasons. The present study investigated the transformation of defatted rice bran into proteins (single cell and extracted protein), soluble and insoluble dietary fiber, and minerals. RESULTS: In a process chain, starch/glucose was enzymatically extracted and converted into single cell protein (Chlorella sorokiniana). Then, rice bran proteins were extracted and partially precipitated. The remaining liquid was ultrafiltered (3 kDa) to obtain a further protein fraction and minerals. The protein fraction contained a considerable amount of soluble dietary fiber. With these steps, around 69% of the rice bran was transformed, resulting in three protein fractions with an average purity of approximately 45% and minerals with a purity of approximately 63%. In a subsequent process, the remaining cake was disintegrated at 95 °C and pH 2. A further 12% of the rice bran could be liquefied. After centrifugation, the supernatant was subjected to ultrafiltration (3 kDa) to obtain soluble dietary fiber in the retentate and minerals in the permeate. However, only around 2% of the rice bran was converted into soluble dietary fiber, whereas the remainder comprised a mixture of minerals and monomeric sugars. CONCLUSION: The process chain can be rearranged and optimized especially to increase the output of soluble dietary fiber and proteins as a result of using the digested monomeric sugars for algae cultivation. At the end of the process, 18% of rice bran remained as an insoluble dietary fiber fraction. © 2019 Society of Chemical Industry.

Disintegration of the agricultural by-product wheat bran under subcritical conditions.

BACKGROUND: The disintegration of destarched wheat bran in water and sulfuric acid (pH 3) under subcritical conditions (275-300 °C) and at short reaction times (1-4 min) was investigated. A cascade process comprising a stepwise separation of the liquid was applied to reduce the formation of undesired degradation products. RESULTS: The highest degree of biomass disintegration (67% dry mass solubilization) was achieved by application of a cascade process at 275 °C (pH 3). Regarding the dissolution of carbohydrates (monomeric and oligomeric form), the total glucose yields remained below 60%, while the total xylose and arabinose yields were about 76% and 67%. Approximately 74% of the protein and 95% of the mineral fraction could be extracted. The application of the cascade process enabled a substantially reduced formation of degradation products. CONCLUSION: When operating hydrothermally and subcritically in order to avoid some problematic aspects of a biorefinery, an extensive disintegration and monomerization of wheat bran and its constituents remains difficult even under the tested conditions (300 °C, pH 3). However, the applied cascade process proved to be useful to increase the yields and to substantially reduce the formation of undesired degradation products. Despite this fact, increased water consumption has to be conceded. © 2018 Society of Chemical Industry.

Fractionation of a galacto-oligosaccharides solution at low and high temperature using nanofiltration.

Like in many applications, solutions of high sugar content can cause serious problems due to microorganism contaminations. Hence, the main aim of this work was to study a nanofiltration process for GOS purification at 5 °C and 60 °C that may circumvent or reduce potential microbial growth. Process performances and rejection behaviors of monosaccharide as well as individual GOS components were compared. Operating at 5 °C is more advantageous especially with respect to the oligosaccharide (OS) recovery yield. Using a NF membrane (NP030) at 45 bar, a product purity of 85% (based on monosaccharide content) and an OS recovery yield of 82% could be achieved. However, a low average permeate flux of 3 L/m2 h had to be accepted. A diafiltration step improved product purity to 90% with 30% losses of OS. A qualitative theoretical discussion shows that a possible change of the pore radius distribution depending on temperature could play a role in solute rejection as well as selectivity.

Wheat bran biorefinery--an insight into the process chain for the production of lactic acid.

The present study investigates a wheat bran biorefinery including major processing steps pre-extraction, pre-treatment and lactic acid fermentation. Concerning the dry mass distribution, during the pre-extraction 32% of the feedstock was recovered, offering some perspectives for applications in food area. The pre-treatment (hydrothermal/enzymatic hydrolysis) of the remaining cake solubilized 34% of dry mass and led to a fermentable sugar concentration of 21g/L. The fermentation resulted in a lactic acid yield of 0.73g/g substrate. Concentrating the fermentation feed via nanofiltration did not improve the lactic acid productivity. Taking into account that Lactobacillus pentosus, a heterofermentative microorganism was used, the dry mass balance revealed a product yield of 47% (32% extract, 15% lactic acid). Based on a theoretical consideration involving a cellulolytic enzyme production (10% feedstock allocation) and lignin utilization, under optimized conditions a maximum product yield of around 80% (35% extract, 39% lactic acid, 6% lignin) could be expected.

Investigations on a wheat bran biorefinery involving organosolv fractionation and enzymatic treatment.

The present study elucidates the organosolv treatment of wheat bran, the major by-product of the milling industry. The influence of temperature (160-200°C) and ethanol concentration (30-60% (w/w)) at a given process time of 30min was investigated. Enzymatic treatments of the organosolv extracts including solid residues led to an overall glucose yield of 75%. The conversion of hemicelluloses into xylose and arabinose was approximately 60% and 45%, respectively. Proteins could be almost completely dissolved, however, practically no free amino acids were obtained. Surprisingly, only around 30% of lignin and 65% of minerals were dissolved. Severe treatment conditions induced the disintegration of fat into glycerol and fatty acids as well as the formation of sugar degradation products. During the lignin precipitation step, proteins partially coprecipitated.

Wheat bran biorefinery: an investigation on the starch derived glucose extraction accompanied by pre- and post-treatment steps.

Wheat bran, a side product of the milling industry, can be considered as a feedstock for biorefineries. Unlike other lignocellulosic feedstock, wheat bran contains a reasonable amount of starch, which is not of recalcitrant nature. Therefore, it can be extracted without a costly pretreatment process. The present work evaluates the extraction of starch derived glucose in relation to a wheat bran biorefinery. The purity of free glucose extracted quantitatively was 44%. The extract was concentrated by threefold via nanofiltration, thereby reaching a glucose concentration of 49 g/L. Hydrothermal treatment (180°C - 20 min) of the starch-free bran did not induce the formation of hydroxymethylfurfural and levulinic acid. Interestingly, the furfural level increased compared to the process, in which bran was treated hydrothermally without a preceding starch extraction. By separation of water-extractables prior to enzymatic hydrolysis, the free glucose purity was increased to 58%, however the yield of glucose decreased to 61%.

Accurate analysis of formose reaction products by LC-UV: an analytical challenge.

This study presents a liquid chromatography-ultraviolet (LC-UV) method for the accurate analysis of formose reaction products with regard to sum parameters. Limitations encountered in gas chromatography (e.g., thermal stability of analytes) were overcome. First, alditols are O-benzoylated and subjected to reversed-phase chromatography. They are then detected by UV and by electrospray ionization-mass spectrometry (ESI-MS) for validation purposes. Compared with standard 2,4-dinitrophenylhydrazine labeling, the accuracy of results from LC-UV is dramatically improved due to enhanced chromatographic resolution and validation by ESI-MS. For the first time ever, LC-UV may be used to accurately quantify 2-hydroxymethylglycerol, a branched chain alditol, D,L-glyceraldehyde, D,L-galactose, which represents the group of D,L-iditol/galactose/glucose/mannose and D,L-erythrose in formose reaction products.

Wheat bran biorefinery--a detailed investigation on hydrothermal and enzymatic treatment.

Due to the enormous quantities arising in the milling industry and its specific properties, wheat bran can be considered as a feedstock for future biorefineries. In the present work, a detailed investigation was carried out on the hydrothermal (140-200°C) and enzymatic treatment of wheat bran. After hydrothermal pretreatment and a subsequent enzymatic hydrolysis a glucose yield of 65% and 90% was achieved, respectively. Interestingly, the hemicelluloses could be disintegrated to monomers only to approx. 50%. About 70% of the proteins were dissolved, however, practically no free amino acids were obtained under given conditions. Severe treatment conditions induce elevated losses of some amino acids. Minerals could be extracted almost completely. To disintegrate fat into glycerol and fatty acids severe process conditions were necessary. The formation of undesired by-products such as furfural or hydroxymethylfurfural starts at approx. 180°C.

Analysis of formose sugar and formaldehyde by high-performance liquid chromatography.

Formose sugar and formaldehyde (HCHO) were analyzed using high-performance liquid chromatography (HPLC) utilizing a CarboPac PA1 column (Dionex) and pulsed amperometric detection. This HPLC system was unsuitable for the analysis of formose sugar and HCHO and thus reducing sugars and unconverted HCHO were determined by endowing them with charges through a derivatization method using 2,4-dinitrophenylhydrazine. The separation and detection of compounds were performed by three Chromolith RP-C18 columns (Merck) and diode array detection, at a wavelength of 360 nm ultraviolet light, respectively. Lower sugars (except HCHO) showed some instabilities when the derivatized samples were kept for the extended periods of time. For C(5) and consecutive higher sugars, a certain derivatization time was necessary. In the present case (formose reaction with partial HCHO conversion), approximately 18 h may be a reasonable compromise for the derivatization reaction. A derivatization agent to compound mole ratio of up to 100:1 was required to complete the derivatization of C(4) and higher sugars. However, the analysis of C(4) and consecutive higher sugars is problematic for example due to overlapping of peaks or branched-chain sugars.

Green biorefinery: separation of lactic acid from grass silage juice by chromatography using neutral polymeric resin.

The aim of this work was to recover lactic acid in undissociated form from grass silage juice. For this aim, chromatographic separation using neutral polymeric resin Amberlite XAD1600 was investigated. Up to now, there is no hint in the literatures about using neutral polymeric resin for lactic acid separation from a mixture. Important factors (flow-rate, concentration of feed and loaded volume) that affect separation performance were firstly investigated with model solutions. The obtained results showed that lactic acid solutions with the purity varying from 93.2% to 99.9% could be obtained at the recovery yields over 99.4%. After that, trials with silage juice were carried out. Due to the complex composition of the feed, the purity of products decreased to 94% at a recovery yield of 97%. Although 99% of inorganic salts and sugars were separated from lactic acid organic acids in general and acetic acid in particular caused a purity problem. It seems that organic acids could not be separated from lactic acid by neutral resin Amberlite XAD1600. Besides the organic acid problem, some amino acids were remained in the products as impurities.

Optimization of an innovative hollow-fiber process to produce lactose-reduced skim milk.

The research field for applications of lactose hydrolysis has been investigated for several decades. Lactose intolerance, improvement for technical processing of solutions containing lactose, and utilization of lactose in whey are the main topics for development of biotechnological processes. We report here the optimization of a hollow-fiber membrane reactor process for enzymatic lactose hydrolysis. Lactase was circulated abluminally during luminal flow of skim milk. The main problem, the growth of microorganisms in the enzyme solution, was minimized by sterile filtration, ultraviolet irradiation, and temperature adjustment. Based on previous experiments at 23 +/- 2 degrees C, further characterization was carried out at 8 +/- 2 degrees C, 15 +/- 2 degrees C (beta-galactosidase), and 58 +/- 2 degrees C (thermostable beta-glycosidase) varying enzyme activity and flow rates. For a cost-effective process, the parameters 15 +/- 2 degrees C, 240 U/mL of beta-galactosidase, an enzyme solution flow rate of 25 L/h, and a skim milk flow rate of about 9 L/h should be used in order to achieve an aimed productivity of 360 g/(L x h) and to run at conditions for the highest process long-term stability.

A new innovative process to produce lactose-reduced skim milk.

The research field for applications for lactose hydrolysis has been investigated for some decades. Lactose intolerance, improvement for technical processing of solutions containing lactose and utilisation of lactose in whey are main topics in development of biotechnological processes. In this article, the establishment of a hollow fiber membrane reactor process for enzymatic lactose hydrolysis is reported. Mesophilic beta-galactosidases were circulated abluminally during luminal flow of skim milk. The main problem, microorganisms growth in the enzyme solution, was minimised by sterile filtration and UV irradiation. In order to characterise the process parameters, such as skim milk concentration, enzyme activity and flow rates were varied. In comparison to a batch process, enzyme activity could be used longer and enzyme rest into the product should not occur. Furthermore, the three-dimensional separation of the substrate from the enzyme solution minimise blocking and washing out effects, which restrict processes with immobilised enzymes. A conversion rate of 78.11% was achieved at a skim milk flow rate of 9.9l h(-1), enzyme activity of 120 Uml(-1) and a temperature of 23+/-2 degrees C in a hollow fiber reactor with a membrane area of 4.9 m2.