Latvian State Institute of Wood Chemistry

Organisms provide some of the most sensitive indicators of climate change and evolutionary responses are becoming apparent in species with short generation times. Large datasets on genetic polymorphism that can provide an historical benchmark against which to test for recent evolutionary responses are very rare, but an exception is found in the brown-lipped banded snail (Cepaea nemoralis). This species is sensitive to its thermal environment and exhibits several polymorphisms of shell colour and banding pattern affecting shell albedo in the majority of populations within its native range in Europe. We tested for evolutionary changes in shell albedo that might have been driven by the warming of the climate in Europe over the last half century by compiling an historical dataset for 6,515 native populations of C. nemoralis and comparing this with new data on nearly 3,000 populations. The new data were sampled mainly in 2009 through the Evolution MegaLab, a citizen science project that engaged thousands of volunteers in 15 countries throughout Europe in the biggest such exercise ever undertaken. A known geographic cline in the frequency of the colour phenotype with the highest albedo (yellow) was shown to have persisted and a difference in colour frequency between woodland and more open habitats was confirmed, but there was no general increase in the frequency of yellow shells. This may have been because snails adapted to a warming climate through behavioural thermoregulation. By contrast, we detected an unexpected decrease in the frequency of Unbanded shells and an increase in the Mid-banded morph. Neither of these evolutionary changes appears to be a direct response to climate change, indicating that the influence of other selective agents, possibly related to changing predation pressure and habitat change with effects on micro-climate.

Biodegradable polymer composites from renewable resources are the next-generation of wood-like materials and are crucial for the development of various industries to meet sustainability goals. Functional applications like packaging, medicine, automotive, construction and sustainable housing are just some that would greatly benefit. Some of the existing industries, like wood plastic composites, already encompass given examples but are dominated by fossil-based polymers that are unsustainable. Thus, there is a background to bring a new perspective approach for the combination of microcrystalline cellulose (MCC) and nanofibrillated cellulose (NFC) fillers in bio-based poly (butylene succinate) matrix (PBS). MCC, NFC and MCC/NFC filler total loading at 40 wt % was used to obtain more insights for wood-like composite applications. The ability to tailor the biodegradable characteristics and the mechanical properties of PBS composites is indispensable for extended applications. Five compositions have been prepared with MCC and NFC fillers using melt blending approach. Young's modulus in tensile test mode and storage modulus at 20 °C in thermo-mechanical analysis have increased about two-fold. Thermal degradation temperature was increased by approximately 60 °C compared to MCC and NFC. Additionally, to estimate the compatibility of the components and morphology of the composite's SEM analysis was performed for fractured surfaces. The contact angle measurements testified the developed matrix interphase. Differential scanning calorimetry evidenced the trans-crystallization of the polymer after filler incorporation; the crystallization temperature shifted to the higher temperature region. The MCC has a stronger effect on the crystallinity degree than NFC filler. PBS disintegrated under composting conditions in a period of 75 days. The NFC/MCC addition facilitated the specimens' decomposition rate up to 60 days.

Biomass is defined as organic matter from living organisms represented in all kingdoms. It is recognized to be an excellent source of proteins, polysaccharides and lipids and, as such, embodies a tailored feedstock for new products and processes to apply in green industries. The industrial processes focused on the valorization of terrestrial biomass are well established, but marine sources still represent an untapped resource. Oceans and seas occupy over 70% of the Earth’s surface and are used intensively in worldwide economies through the fishery industry, as logistical routes, for mining ores and exploitation of fossil fuels, among others. All these activities produce waste. The other source of unused biomass derives from the beach wrack or washed-ashore organic material, especially in highly eutrophicated marine ecosystems. The development of high-added-value products from these side streams has been given priority in recent years due to the detection of a broad range of biopolymers, multiple nutrients and functional compounds that could find applications for human consumption or use in livestock/pet food, pharmaceutical and other industries. This review comprises a broad thematic approach in marine waste valorization, addressing the main achievements in marine biotechnology for advancing the circular economy, ranging from bioremediation applications for pollution treatment to energy and valorization for biomedical applications. It also includes a broad overview of the valorization of side streams in three selected case study areas: Norway, Scotland, and the Baltic Sea.

New cold‐pressed oil recovered from seeds of Japanese quince ( Chaenomeles japonica (Thunb.) Lindl. ex Spach, family: Rosaceae), obtained as a by‐product of fruit processing, was characterized and compared with nine well‐known oils. The Japanese quince seed oil had the highest amounts of tocopherols, β‐carotene, and total phenolic compounds (726.20; 10.77 and 64.03 mg/kg, respectively) and the lowest amount of chlorophyll (0.12 mg/kg) and peroxide value (0.59 mEq O 2 /kg) compared to sesame, poppy, peanut, flaxseed, pumpkin, sunflower, almond, hazelnut, and walnut oils. A correlation was found between the total contents of tocochromanols, β‐carotene, phenolic compounds, and the radical‐scavenging capacity of the oils (0.94, 0.68, 0.63, respectively), and also between the amount of chlorophyll and the CIE a* coordinate (0.80) and the amount of β‐carotene and the CIE b* coordinate (0.47). In Japanese quince seed oil, 13 fatty acids were identified with three predominating: palmitic acid (10.07%), oleic acid (34.55%), and linoleic acid (52.35%). The highest consumer acceptance was noted for hazelnut and walnut oils, while it was lowest for the poppy and flaxseed oils. Amygdalin was not detected in the Japanese quince seed oil. Practical applications: This study demonstrated that Japanese quince seed oil is a richer source of nutritional bio‐components than other commercial cold‐pressed oils. The positive results of sensory evaluation and the absence of amygdalin in the oil indicates its potential future use in food. Moreover, it is recovered from by‐products of fruit industry; therefore, its utilization in obtaining of new, healthy products ensures environmental sustainability and a more effective use of harvested plant material.

The aim of the study was to characterize and compare films made of cellulose nanocrystals (CNC), nano-fibrils (CNF), and bacterial nanocellulose (BNC) in combination with chitosan and alginate in terms of applicability for potential food packaging applications. In total, 25 different formulations were made and evaluated, and seven biopolymer films with the best mechanical performance (tensile strength, strain)-alginate, alginate with 5% CNC, chitosan, chitosan with 3% CNC, BNC with and without glycerol, and CNF with glycerol-were selected and investigated regarding morphology (SEM), density, contact angle, surface energy, water absorption, and oxygen and water barrier properties. Studies revealed that polysaccharide-based films with added CNC are the most suitable for packaging purposes, and better dispersing of nanocellulose in chitosan than in alginate was observed. Results showed an increase in hydrophobicity (increase of contact angle and reduced moisture absorption) of chitosan and alginate films with the addition of CNC, and chitosan with 3% CNC had the highest contact angle, 108 ± 2, and 15% lower moisture absorption compared to pure chitosan. Overall, the ability of nanocellulose additives to preserve the structure and function of chitosan and alginate materials in a humid environment was convincingly demonstrated. Barrier properties were improved by combining the biopolymers, and water vapor transmission rate (WVTR) was reduced by 15-45% and oxygen permeability (OTR) up to 45% by adding nanocellulose compared to single biopolymer formulations. It was concluded that with a good oxygen barrier, a water barrier that is comparable to PLA, and good mechanical properties, biopolymer films would be a good alternative to conventional plastic packaging used for ready-to-eat foods with short storage time.

BACKGROUND: The health-promoting properties of apples are directly related to the biologically active compounds that they contain, such as polyphenols. The objective of this study was to prepare a low-sugar, fibre- and phlorizin-enriched powder from unripe apples and to gain insight regarding its anti-hyperglycaemic activity in healthy volunteers. RESULTS: The unripe apples (Malus domestica Borkh.) were collected 30 days after the full bloom day; blanched and pressed to obtain apple pomace which was then processed with a food cutter, oven-dried and milled to prepare apple powder. The concentrations of total sugars, water-soluble pectin and phlorizin in the apple preparation were 153.44 ± 2.46, 27.73 ± 0.51 and 12.61 ± 0.15 g kg(-1), respectively. Acute ingestion of the apple preparation improved glucose metabolism in the oral glucose tolerance test (OGTT) in six healthy volunteers by reducing the postprandial glucose response at 15 to 30 min by approximately two-fold (P < 0.05) and by increasing urinary glucose excretion during the 2- to 4-h interval of the OGTT by five-fold (P < 0.05). CONCLUSION: The results obtained indicate that the dried and powdered pomace of unripe apples can be used as a health-promoting natural product for the reduction of postprandial glycaemia and to improve the health of patients with diabetes.

Abstract Masuko refining of unbleached kraft birch pulp has been noted to result in more thorough fibrillation than the refining of its bleached counterpart. This result is observed through different fractionation behavior of once refined pulps and is further supported by different relative changes in pulp viscosity. The formation of mechanoradicals during refining is observed with electron paramagnetic resonance spectroscopy, and the role of lignin and hemicelluloses [quantified using kappa number determination and UV resonance Raman (UVRR) spectroscopy] in the progress of refining is discussed. Lignin, a known antioxidant, is capable of stabilizing radicals, which could potentially counteract recombination reactions between highly reactive cellulose radicals. On the other hand, lignin’s ability to promote fibrillation could also lie in its amorphous nature and not solely in its antioxidant characteristics. Furthermore, bleaching removes not only lignin but also hemicelluloses, which affects both the charge density and the structure of the fiber material, and this is another likely contributor to the easier fibrillation of lignin-containing pulps.

Eight tocochromanols (α, β, γ, and δ homologues of tocopherol and tocotrienol) naturally occurring in foods were successfully separated within a 13‐min run in the RP‐HPLC mode. Analytes were separated on the Phenomenex Luna PFP column filled with the pentafluorophenyl stationary phase (3 µm, 150 mm × 4.6 mm) using the mobile phase containing methanol:water (93:7 v/v) with an elution flow rate of 1 ml/min and column oven temperature of 40°C. The method was rapid, linear, accurate, and precise with detection limits in the range of 0.000184–0.000605 µg, preventing analyte losses due direct dissolution in 2‐propanol. The developed RP‐HPLC method in comparison with the NP‐HPLC mode had a significantly higher sensitivity, speed, and repeatability, but primarily it protected against the loss of analytes and thus reduced the risk of possible error measurements. It was found that tocopherol contents in the tested butter samples amounted to 2.00–16.92 mg/100 g for samples coming from Poland and 2.61–2.98 mg/100 g for samples from Latvia, respectively. The method is characterized by simplicity of implementation and it was successfully applied in the determination of tocochromanols in butter to verify product authenticity. Practical applications: To ensure consumers' protection, food products should be subject to continuous quality and authenticity control. One way to determine butter authenticity is to analyze native tocochromanol contents. This paper describes a simple and fast method determine plant oils added to milk fat with the use of RP‐HPLC techniques. Eight tocochromanols (α, β, γ, and δ homologues of tocopherol and tocotrienol) naturally occurring in foods were successfully separated within by RP‐HPLC. The method is rapid, linear, accurate, and precise with detection limits in the range of 0.184–0.605 μg. The method was successfully applied to determine tocochromanols in butter to verify product authenticity.

The profiles of tocopherols and tocotrienols (vitamin E) in the seed oils recovered from apple ( Malus domestica Borkh.), canary melon ( Cucumis melo L.), gooseberry ( Ribes uva‐crispa L.), grape ( Vitis vinifera L.), Japanese quince ( Chaenomeles japonica ), pomegranate ( Punica granatum L.), red currant ( Ribes rubrum L.), sea buckthorn ( Hippophae rhamnoides L.), and watermelon ( Citrullus lanatus ) by‐products of the fruit industry were studied. The highest concentration of tocochromanols was found in pomegranate seed oil (398.73 mg/100 g) and the lowest in gooseberry seed oil (69.13 mg/100 g). The γ and α homologues were the predominant forms of tocopherol and tocotrienol in all fruit seed oils studied. The pomegranate, canary melon, watermelon, gooseberry and red currants seed oils contained mainly γ ‐tocopherol (382.69, 63.08, 111.01, 60.35, and 156.39 mg/100 g, respectively). In the apple, sea buckthorn and Japanese quince seed oils, α ‐tocopherol was the predominant tocochromanol (58.77, 121.79, and 198.94 mg/100 g, respectively). High concentrations of tocotrienol homologes ( γ and α ) (49.49 and 34.53 mg/100 g, respectively) were found only in grape seed oil. A significant correlation ( r = 0.994, p &lt; 0.00001) between the total content of tocochromanols in the seed oils and scavenging of the free radical DPPH was found. Practical applications This study demonstrated that seed oils recovered from industrial fruit by‐products generated by the food industry are valuable source of tocochromanols. Therefore, fruit seed oils may be successfully applied to obtain new products rich in vitamin E for the food, pharmaceutical and cosmetic industries, with environmental sustainability benefits and a more effective use of harvested plant material. The profiles of tocopherols and tocotrienols in the seed oils recovered from apple ( Malus domestica Borkh.), canary melon ( Cucumis melo L.), gooseberry ( Ribes uva‐crispa L.), grape ( Vitis vinifera L.), Japanese quince ( Chaenomeles japonica (Thunb.) Lindl. ex Spach), pomegranate ( Punica granatum L.), red currant ( Ribes rubrum L.), sea buckthorn ( Hippophae rhamnoides L.) and watermelon ( Citrullus lanatus (Thunb.) Matsum. &amp; Nakai) by‐products of the fruit industry were studied. The homologues γ and α were predominant for both, tocopherols and tocotrienols. However, the concentration and composition of tocochromanols varied considerably in seed oils recovered from industrial fruit by‐products.

The antioxidant capacity (AC) of boiled-type coffee brews (CB) and phenolic acids (PA) isolated from them, obtained from the caffeinated and decaffeinated beans of different geographical origins and species and with different roasting degrees, was examined. The AC of PA and CB samples was tested in five antioxidant assays: a total antioxidants reducing capacity assay using a Folin–Ciocalteu reagent (FCR), a ferric ion reducing antioxidant power (FRAP) assay, a DPPH· radical-scavenging activity (DPPH) assay, a metal chelating activity (MCA) assay and a total radical trapping antioxidant parameter (TRAP) assay. In most samples, the total amount of phenolic acids, determined by HPLC, decreased with the increasing degree of roasting the coffee beans, leading to reduced AC. All used methods showed that CB exhibits higher AC compared with the PA samples. Phenolic acids isolated from CB samples have the main contribution (on average over 95 and 84 % in green and roasted coffee extracts, respectively) in AC of the CB samples in FCR, FRAP and TRAP assays, whereas in DPPH and MCA tests, the phenolic acid contribution in AC of CB samples was below 50 % (on average over 36 and 45 % in green and roasted coffee extracts, respectively). Significant differences between the AC values determined for CB and PA samples were noticed only for the MCA and DPPH methods which reflect the different molecular mechanisms underlying each of the assays. Additionally, the statistical methods, including principal component analysis, applied to results of antioxidant capacity obtained with different analytical techniques confirmed their feasibility to distinguish between coffee brews with different degrees of roasting, regardless of coffee origin.

Developing polyols derived from natural sources and recycling materials attracts great interest for use in replacing petroleum-based polyols in polyurethane production. In this study, rigid polyurethane (PUR) foams with various isocyanate indices were obtained from polyols based on rapeseed oil and polyethylene terephthalate (RO/PET). The various properties of the prepared PUR foams were investigated, and the effect of the isocyanate index was evaluated. The closed-cell content and water absorption were not impacted by the change of the isocyanate index. The most significant effect of increasing the isocyanate index was on the dimensional stability of the resulting foams. This is due to the increased crosslink density, as evidenced by the increased formation of isocyanurate and increase of the glass transition temperature. Additionally, the influence on compression strength, modulus, and long-term thermal conductivity were evaluated and compared with reference PUR foams from commercially available polyols. Rigid PUR foams from RO/PET polyol were found to be competitive with reference materials and could be used as thermal insulation material.

Fractionation of softwood and hardwood LignoBoost kraft lignins, using sequential extraction with organic solvents of increasing hydrogen-bonding ability (dichloromethane, n-propanol, and methanol), was carried out. Using SEC, analytical pyrolysis, FTIR and UV/VIS spectroscopy, and chemical analytical methods, four fractions were obtained and characterized in terms of their yield, composition, functionality, lignin structural features, and antioxidant properties. In tests with free radicals (ABTS●+, DPPH●, O2●-) and the ORAC (oxygen radical absorbance capacity) assay, the high radical scavenging capacity of the lignin’s soluble fractions was demonstrated. The antioxidant activity of the fractions was tested by their influence on thermo-oxidative destruction of model polyurethane elastomers. The TGA data clearly revealed the antioxidant effect of the three fractions, with the most prominent activity for the propanol-soluble fraction. The dichloromethane fraction has potential as an antioxidant for non-polar products. Novel correlations between lignin’s structural features and its radical scavenging activity were found that can be used for tuning lignin’s antioxidant properties.

There is a major international effort to improve the availability of data for life cycle assessment (LCA), as these assessments have become one of the main pillars driving European policy with respect to the sustainable use of resources. However, there is still a lack of data even for Europe. This study presents a cradle-to-farm gate assessment, or LCA, of winter and spring rapeseed produced in the northern European country of Latvia. The LCA model is based on an in-depth and up-to-date agricultural practice used in the region and covers the time span of 2008–2016. An LCA of rapeseed oil produced by cold pressing was carried out. The environmental impact assessment was calculated with the ReCiPe impact assessment method version 1.03, a hierarchical (H) perspective, along with the cumulative energy demand method v1.11. Cultivation of winter rapeseed has a lower environmental impact than cultivation of spring rapeseed due to higher agricultural inputs and higher yield. The greatest impact is on human health. Mineral fertilizers (production and application) and agricultural machinery are responsible for the greatest environmental impact. The results for the mill stage of rapeseed oil demonstrated that the choice of the allocation method has a significant impact on the environmental performance results.

Studies on the effect of the foams’ polymeric matrix’ properties on the tension and compression properties of pour rigid polyurethane (PUR) foams, apparent core density 65—70 kg/m 3 , at 296 and 77 K were carried out. PUR foams were produced by the hand mixing method from polyol systems that comprised polyether, polyester polyols, and chain extenders. To produce PUR foams, crude MDI was used, and Solkane 365 mfc/227 ea was used as a blowing agent. The molecular weight per branching unit (M c ) of the polymeric matrix of PUR foams was varied in the range 300—1150. Cohesion energy densities of the blocks forming the polymeric matrix were calculated. The effect of M c on the formation of hydrogen bonds between the urethane groups was estimated from FTIR spectroscopy data and ratio NH bonded /NH free . It has been found that, with increasing polymeric matrix’ M c , the tensile strength and elongation at break of PUR foams at 296 and 77 K increases, while Young’s modulus decreases. The increase in the parameter M c promotes the decrease in the compressive strength and modulus of elasticity of PUR foams at 296 K, while compressive strength indices at 77 K are higher for the foams, whose polymeric matrix has the highest M c . With increasing polymeric matrix’ M c , the concentration of the urethane groups bonded with hydrogen bonds increases. Structural and mechanical properties of layered spray polyurethane foams, apparent core density approx. 48 kg/m 3 , having two layers and polymeric matrix’ M c = 740 were investigated.

Ammonium persulfate has been known as an agent for obtaining nanocellulose in recent years, however most research has focused on producing cellulose nanocrystals. A lack of research about combined ammonium persulfate oxidation and common mechanical treatment in order to obtain cellulose nanofibrils has been identified. The objective of this research was to obtain and investigate carboxylated cellulose nanofibrils produced by ammonium persulfate oxidation combined with ultrasonic and mechanical treatment. Light microscopy, atomic force microscopy (AFM), powder X-Ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Zeta potential measurements were applied during this research. The carboxylated cellulose suspension of different fractions including nanofibrils, microfibrils and bundles were produced from bleached birch Kraft pulp fibers using chemical pretreatment with ammonium persulfate solution and further defibrillation using consequent mechanical treatment in a high shear laboratory mixer and ultrasonication. The characteristics of the obtained nanofibrils were: diameter 20–300 nm, crystallinity index 74.3%, Zeta potential −26.9 ± 1.8 mV, clear FTIR peak at 1740 cm−1 indicating the C=O stretching vibrations, and lower thermostability in comparison to the Kraft pulp was observed. The proposed method can be used to produce cellulose nanofibrils with defined crystallinity.

Abstract The antioxidant activities (AoAs) of 50 different technical lignins have been determined. The lignins of various botanical origins (annual plants, coniferous trees, and deciduous trees) were isolated and fractionated by different techniques (delignification by alkali, kraft process, fast pyrolysis, and hydrolysis). The structure and the functionality of lignins were characterized by functional group analyses (phenolic OH, carboxyl, and methoxyl groups), analytical pyrolysis pyrolysis/gas chromatography/mass spectrometry/flame ionization detector (Py-GC/MS/FID), electron paramagnetic resonance, size exclusion chromatography, and titrimetric methods, and the AoAs were evaluated as the capacity to scavenge the DPPH · and ABTS ·+ free radicals. The relationship between the lignin structure and the AoA was characterized by pair correlation, partial correlation, and multivariate regression analyses, including correlated components regression. The results were compared with those of lignin model compounds and low molecular weight phenylpropanoids. It has been shown that molecular weight does not influence essentially the AoA of lignins. There is a relationship between the activities of low and high molecular weight polyphenols; their mechanisms of action are also similar. The structure-related AoA of lignins has been quantified for the first time.

In recent decades, vegetable oils as a potential replacement for petrochemical materials have been extensively studied. Tall oil (crude tall oil, distilled tall oil, tall oil fatty acids, and rosin acids) is a good source to be turned into polymeric materials. Unlike vegetable oils, tall oil is considered as lignocellulosic plant biomass waste and is considered to be the second-generation raw material, thus it is not competing with the food and feed chain. The main purpose of this review article is to identify in what kind of polymeric materials wood biomass-based fatty acids and rosin acids have been applied and their impact on the properties.

Tocochromanols composition in apple seeds, obtained as a by-product during the fruit salad and juice production, of twelve varieties - seven crab apple (‘Kerr’, ‘Kuku’, ‘Quaker Beauty’, ‘Riku’, ‘Ritika’, ‘Ruti’ and K-8/9-24) and five dessert apples (‘Antej’, ‘Beforest’, ‘Kent’, ‘Sinap Orlovskij’ and ‘Zarja Alatau’) were studied. Tocopherols and tocotrienols were isolated using the micro-saponification method of high precision and accuracy and they were analysedanalysed by rapid RP-HPLC/FLD and RP-UPLC-ESI/MSn. Four tocopherols, with predominance of homologues α and β, were detected in each tested sample. The seeds from two apple cultivars ‘Antej’ and ‘Beforest’ were characterized by unique and similar ratios of all four tocopherol homologues α:β:γ:δ (1.7:1.5:1.3:1.0 and 2.1:2.0:1.3:1.0, respectively). The concentration range of individual tocopherol homologues (α, β, γ and δ) in apple seeds were as follows: 17.22–25.79, 7.53–29.05, 0.61–13.82 and 0.16–10.79 mg/100 g dry weight basis (dwb), respectively. Moreover, three tocotrienols (α, β and γ) were identified in lesser amounts (0.02–0.74 mg/100 g dwb). Use of apple seeds to isolate tocopherol homologues can ensure better environmental sustainability and effective use of natural plant material.

This study investigates biofuel production from wheat straw hydrolysate, from which furfural was extracted using a patented method developed at the Latvian State Institute of Wood Chemistry. The solid remainder after furfural extraction, corresponding to 67.6% of the wheat straw dry matter, contained 69.9% cellulose of which 4% was decomposed during the furfural extraction and 26.3% lignin. Enzymatic hydrolysis released 44% of the glucose monomers in the cellulose. The resulting hydrolysate contained mainly glucose and very little amount of acetic acid. Xylose was not detectable. Consequently, the undiluted hydrolysate did not inhibit growth of yeast strains belonging to Saccharomyces cerevisiae, Lipomyces starkeyi, and Rhodotorula babjevae. In the fermentations, average final ethanol concentrations of 23.85 g/l were obtained, corresponding to a yield of 0.53 g ethanol per g released glucose. L. starkeyi generated lipids with a rate of 0.08 g/h and a yield of 0.09 g per g consumed glucose. R. babjevae produced lipids with a rate of 0.18 g/h and a yield of 0.17 per g consumed glucose. In both yeasts, desaturation increased during cultivation. Remarkably, the R. babjevae strain used in this study produced considerable amounts of heptadecenoic, α,- and γ-linolenic acid.

The fed-batch cultivation is in many ways a benchmark for fermentation processes, and it has been an attractive choice for the biotechnological production of various products in the past decades. The majority of biopharmaceuticals that are presently undergoing clinical trials or are available on the market are manufactured through fed-batch fermentations. A crucial process parameter in fed-batch cultivations is the substrate feed rate, which directly influences the overall process productivity, product quality and process repeatability; henceforth, effective control of this parameter is imperative for a successful fed-batch fermentation process. Two distinct control strategies can be distinguished—open-loop and closed-loop (feedback) control. Each of these methods has its own set of benefits, limitations and suitability for specific bioprocesses. This article surveys and compares the most popular open- and closed-loop methods for substrate feed rate control in fed-batch fermentations. Emphasis is placed on model-predictive feed rate control (MPC)—a stand out among other methods that offers a promising application perspective. The authors also demonstrate a practical example of the implementation of a robust, flexible MPC solution that is suitable for various cultures and runs on standard computer hardware, thus overcoming one of the main reported MPC drawbacks—high computational requirements.