Type Of Inoculum Research Articles

EFFECT OF FERMENTATION PROCESSES ON PHENOLIC CONTENT AND ANTIOXIDANT ACTIVITY DURING PRODUCTION OF BLACK CARROT VINEGAR

Black carrots and black carrot-derived products have gained great popularity in recent years due to their significant content of health-promoting bioactive compounds. Therefore, this study focuses on the production of vinegar from black carrot juice (BCJ) derived from black carrot juice concentrate (BCJC), to attain a food product with nutritional added value. In this study, the effect of alcoholic fermentation by Saccharomyces cerevisiae and acetic acid fermentation by four different vinegar starters (grape, apple, alcohol vinegar, and the mixture of grape and apple vinegar) on some physicochemical properties (pH, total acidity, total dry matter, reducing sugar, total phenolics, and antioxidant activity) of BCJ was investigated. The results obtained indicated that processing the BCJ into black carrot wine (BCW) led to an overall reduction of only 4% in total phenolic contents, and a further decrease of 21-32% in total phenolic content was observed in black carrot vinegars (BCVs) due to the acetification process, on a weight-to-volume basis (mg/L). A similar decreasing trend was also determined for the antioxidant activity throughout the vinegar production process. Total phenolic content was not affected by inoculation with any of the seed vinegars since the difference between the total phenolic contents with respect to the four different vinegar starters was statistically insignificant (P > 0.05). In general, the BCW and BCVs (regardless of the type of inoculum) produced in this study exhibited better bioactive properties compared to their commercial counterparts (C-BCW and C-BCV). In conclusion, vinegar was successfully produced from black carrot by retaining a considerable amount of its nutraceutical components

Effect of inoculum composition on the microbial community involved in the anaerobic digestion of sugarcane bagasse

ABSTRACT In anaerobic digestion (AD), the choice of inoculum type seems to be relevant for methane production for complex substrates, such as lignocellulosic material. Previous work demonstrated that the addition of fresh manure and ruminal fluid to anaerobic sludge improved methane productivity and kinetics of AD of crude sugarcane bagasse (CSB). Considering that the improvement of methane production could be a result of a more adapted microbial community, the present study performed the Next Generation Sequencing analysis to identify changes in the microbiome of anaerobic sludge inoculum, resulting from fresh manure and ruminal fluid addition. In comparison with AD performed only with anaerobic sludge inoculum (50:50, U), accumulated methane production was 15% higher with anaerobic sludge plus ruminal fluid inoculum (50:50, UR) and even higher (68%) with anaerobic sludge with fresh bovine manure inoculum (50:50, UFM), reaching the value of 143 NmLCH4.gVS −1. Clostridium species were highly abundant in all inocula, playing an important role during the hydrolysis and fermentation of CSB, and detoxifying potential inhibitors. Microbial composition also revealed the occurrence of Pseudomonas and Anaerobaculum at UFM inoculum that seem to have contributed to the higher methane production rate, mainly due to their hydrolytic and fermentative ability on lignocellulosic substrates. On the other hand, the presence of Alcaligenes might have had a negative effect on methane production due to their ability to perform methane oxidation.

Airborne versus soilborne inoculum: White mould, where do you come from?

AbstractIdentifying the sources of fungal inoculum that induces epidemics is instrumental to managing crop health in a more efficient way by implementing prophylactic methods and by using better targeted biocontrol and fungicide applications. For some phytopathogenic fungi, this identification is hampered by the multiplicity of inoculum types. This is the case for Sclerotinia sclerotiorum, the agent of white mould, which can produce ascospores disseminated via the atmosphere, sclerotia stored in the soil and mycelium in plant debris of a large variety of hosts. The present study aims to assess the relative importance of airborne and soilborne inocula in white mould disease development and its persistence across two crop seasons. S. sclerotiorum isolates were collected from air, soil and carrot plants during two crop seasons in south‐western France and genotyped with 16 microsatellite markers. Among the 490 isolates, 162 clonal lineages were identified. The genetic characteristics did not differ significantly among isolates collected from air, soil and carrots. The epidemics of white mould on carrots were initiated either by airborne inoculum or by soilborne inoculum. It also appears that some isolates from airborne inoculum persisted from year to year.

Influence of Inoculum Type on Volatile Fatty Acid and Methane Production in Short-Term Anaerobic Food Waste Digestion Tests

Influence of Inoculum Type on Volatile Fatty Acid and Methane Production in Short-Term Anaerobic Food Waste Digestion Tests

Thermophilic dark fermentation fast start-up of hydrogen production with substrate concentration regulation and moderate pretreatment inoculum

Accelerating start-up of thermophilic dark fermentation would improve hydrogen production efficiency was investigated. To find an efficient method for accelerating start-up and explore the effect of inoculum type for hydrogen production system, three thermophilic hydrogen production EGSB (expanded granular sludge bed) reactors equipped with flocculent or granular sludge using different startup modes were constructed in this study. Among three reactors under butyric acid type of fermentation, EGSB3 (startup mode: pretreated granular sludge as inoculum and regulated substrate concentration) was the most efficient one with shortest start-up time (13 days) and maximum hydrogen production (1.64 mol H2/mol glucose). EGSB1 (startup mode: pretreated flocculent sludge as inoculum and regulated substrate concentration) was started up in 27 days at 1.27 mol H2/mol glucose in maximum. While EGSB2 (startup mode: original granular sludge as inoculum and without regulating substrate concentration) took 46 days for start-up and the 1.6 mol H2/mol glucose hydrogen producing rate was obtained. After start-up, the dominant hydrogen production bacteria were Thermoanaerobacterium thermosaccharolyticum strain TG57 in three reactors. EGSB3 reactor owned the most proportion with 53.21 % than others. In all, mild pretreatment and regulating substrate concentration for granular sludge would be benefit for fast startup of thermophilic dark fermentation hydrogen production leading to shortest startup time, high hydrogen production efficiency and most functional microorganism.

Exploring the metabolic capabilities of purple phototrophic bacteria during piggery wastewater treatment

Purple phototrophic bacteria (PPB) are receiving an increasing attention due to their extraordinary metabolic capabilities for nutrient and carbon recovery from wastewaters. Batch experiments were herein performed to assess the influence of the type of radiation (photosynthetic active radiation (PAR), near-infrared radiation (NIR) and PAR using an UV-VIS absorbing filter), temperature (13 °C and 30 °C), type of metabolism (photoheterotrophic and chemoheterotrophic), type of inoculum (mixed culture and pure strain Rhodopseudomonas palustris) and wastewater load (1:5 and 1:10 dilutions) during piggery wastewater (PWW) treatment by PPB. The use of UV-VIS filtered PAR supported both a high content of bacteriochlorophyll in PPB and the highest total organic carbon (TOC) and total nitrogen (TN) removal efficiency (RE) (74 % and 37 %, respectively), but at lower maximum removal rates. Interestingly, PPB exhibited similar TOC-REs and TN-REs (73 % and 37 %, respectively) at 13 °C than at 30 °C (71 % and 45 %, respectively), at similar removal rates. Mixed cultures of PPB achieved a higher nutrient assimilation rate than R. palustris, supporting a total assimilation of the volatile fatty acids present in 10 folds diluted PWW. In brief, mixed cultures of PPB were highly efficient during PWW treatment, regardless of the type of radiation and temperature under photoheterotrophic growth.

Efecto del inóculo (líquido ruminal o excreta) sobre la producción de gas in vitro en alimentos para ovinos

An experiment was carried out with the objective of evaluating the effect of two types of inocula from Saint Croix sheep (T1: ruminal fluid, T2: excreta with yeast), in two types of feed with different proportions of concentrate (C) and forage (F), (75C:25F; 25C:75F), on gas production at 24, 36 and 48 h of incubation (in duplicate) in 100 mL syringes (n = 3 replicates per diet), in order to determine in a factorial arrangement 2 X 2, (with two inocula and two diets), if the excreta can replace ruminal fluid as inoculum in in vitro gas production. Gas production was higher with ruminal fluid than with excreta, and with the high-concentrate diet. In conclusion, the excreta inoculum with yeast can be used to estimate the gas production obtained with ruminal fluid in in vitro incubations of feed for sheep.

Experimental and kinetic studies of biogas production from petroleum oily sludge by anaerobic co-digestion with animals’ dung at thermophilic conditions

Abstract Anaerobic co-digestion technology is widely used for biogas generation from organic wastes. In this study, co-digestion of petroleum oily sludge (POS) for biogas production in bench-scale anaerobic digesters at thermophilic conditions was investigated. The effects of inoculum type on the biogas production were considered. Three types of inoculums were examined individually for the co-digestion of POS which were; poultry manure, cattle manure, and cow dung. The results revealed that the biogas production from poultry manure, cattle manure, and cow dung exceeded its production from uninoculated POS by 64.6, 20.94 and 6.1% respectively. Effect of C/N on the co-digestion process was also considered in this study. Modified Gompertz model was applied to describe the kinetic of the co-digestion process. The predicted and experimental results of biogas generation were fitted well with coefficients of determination > 0.96 indicating appropriate conditions of the co-digestion process. Statistical analysis was performed to estimate if there were significant differences in terms of cumulative biogas yield. A significance level value of < 0.05 was obtained.

The Potential of Glutinous Rice Tape Added with Lactobacillus plantarum Dad-13 and Saccharomyces boulardii as a Probiotic Food

Glutinous rice tape circulating in the community generally does not contain probiotic cells. However, adding Lactobacillus plantarum Dad-13 and Saccharomyces boulardii can increase its potential as a probiotic food. This study is aimed to determine the effect of using glutinous rice varieties and the addition of probiotic cells on the number of lactic acid bacteria (LAB) and yeast, levels of anthocyanins, antioxidant activity, as well as the preference level of glutinous rice tape produced. A completely randomized design with a factorial pattern was used in this study. The first factor was glutinous rice varieties (white and black), while the second was the probiotic inoculum type (Lactobacillus plantarum Dad 13 and Saccharomyces boulardii) which were added simultaneously or individually. The result show that adding the probiotic cells simultaneously or individually in the production of white and black glutinous rice tape increased the LAB amount by 2 log cycles and yeast by 1 log cycle. The addition of Saccharomyces boulardii together with Lactobacillus plantarum Dad-13, or individually, resulted in higher anthocyanin levels in black glutinous rice tape than white glutinous tape. The antioxidant activity of white glutinous rice tape was improved by the addition of probiotic cells. For the black glutinous rice tape, the antioxidant activity (87.57-88.61 %RSA) was higher than the activity of white glutinous rice tape (15.58-51.22 %RSA). Furthermore, adding Lactobacillus plantarum Dad-13 simultaneously with Saccharomyces boulardii increased the preference level on aroma, color, taste, texture, and overall, and produced the white glutinous rice tape that the panelists most favored.

Evaluation of the pathogenicity of chrysanthemum stunt viroid variants against dahlia under different conditions

AbstractChrysanthemum stunt viroid (CSVd) is an important pathogen that decreases dahlia yields due to stunting symptoms. Here, we evaluated the effect of nucleotide sequence of CSVd, cultivation conditions, inoculum type and infection timing on CSVd‐infected dahlia growth. Inoculation with CSVd after planting resulted in reduced plant height in the second cut flower, but not the first, indicating that the infection may affect the growth of dahlias after approximately 3–5 months. Additionally, there was no significant difference in the degree of symptom severity among the plants infected with the two types of inoculum, synthesized CSVd RNA and CSVd‐infected plant sap. All three CSVd variants affected the growth of dahlias. The reduction in plant height was almost similar among the three variants. However, the reduction in plant fresh weight and compound leaf size in variant JP1 was significantly higher than that in the other variants in the spring experiment. The rates of blown centre in JP1 were also higher than those in the other variants in the spring and winter experiments under the 14.5‐h photoperiod. These results suggest that JP1 is a more severe variant than JP2 and JP3. Dark period interruption improved the reduction in plant height and weight and flower weight, as well as the rate of blown centre in CSVd‐infected dahlias in the winter experiment compared with the 14.5‐h photoperiod. Our results indicate that the three CSVd variants incite stunting symptoms in dahlias and nucleotide sequence of CSVd, photoperiod and infection timing affect the degree of symptom severity.

Effect of Endogenous Methane Production: A Step Forward in the Validation of Biochemical Methane Potential (BMP) Tests

This work evaluates the influence of the inoculum type, the pre-consumption of the residual substrate and the ratio of blanks’ headspace volume to working volume (Hv Wv−1, 0.6 to 10) on Biochemical Methane Potential (BMP) measurements when methane is monitored by gas chromatography. Different inocula were tested: digested sewage sludge—DSS, granular sludge—GS and fresh dairy manure—DM. Microcrystalline cellulose was used as the substrate. BMP surpassed the maximum theoretical value (BMPmax = 414 L kg−1) when methane produced in the blanks was not discounted, showing that degassing cannot stand alone as an alternative to the procedure of discounting the inoculum’s background production. Still, when the residual substrate concentration is high (e.g., in DM), degassing is mandatory because methane produced from its digestion will conceal the methane produced from the substrate in the BMP determination. For inocula with a low residual substrate (e.g., GS), short degassing periods are recommended in order to avoid detrimental effects on methanogenic activity. For moderate residual substrate concentrations (e.g., DSS), BMP values closer to BMPmax (90–97%) were achieved after degassing and discounting the blanks with lower Hv Wv−1. For higher Hv ∙ Wv−1, less accurate quantification occurred, likely due to error propagation. Proper inoculum pre-incubation time and discounting the methane production from blanks with low Hv Wv−1 (adjusted according to the estimated background methane) are essential for accurate BMP determinations.

Effectiveness of two UV-C light-emitting diodes (LED) systems in inactivating fungal conidia on polyethylene terephthalate

The present study aimed to assess the effects of two UV-C LED systems on three food-spoilage fungi (Hyphopichia burtonii, Penicillium brevicompactum, Aspergillus brasiliensis) that can contaminate food packaging materials. The UV-C LED systems were used at two distinct light intensities (9.0 mW/cm2 and 5.5 mW/cm2) for up to 800 s. Fungal conidia were deposited on polyethylene terephthalate lids as either a single (4–5 log CFU/lid) or a multiple layer of cells (5–6 log CFU/lid) to evaluate any difference due to a potential “shadow effect”. In the tests performed, A. brasiliensis was the most resistant fungus to the effects of UV-C LED irradiation, with its 1D-value varying from 23 to 58 s (9.0 mW/cm2) and from 46 to 58 s (5.5 mW/cm2) regardless of the light source used or the type of inoculum. In contrast, H. burtonii and P. brevicompactum were inactivated within 5 s when a single layer was used, whereas their 1D-values were equal to 2–4 s (H. burtonii) and to 3–13 s (P. brevicompactum) when a multilayer was tested. Given the low fungal contamination of food packaging devices and the possibility of developing tailored LED systems, UV-C LED technology was confirmed as an interesting method of sanitization for food packaging.Industrial relevance: This study provides data on the behaviour of two different UV-C LED systems in inactivating fungal conidia on polyethylene terephthalate surfaces. This study helps to understand how specific factors (e.g., spatial arrangement of cells; fluctuating fungal loads on packaging devices) can influence the UV-C LED system performance and therefore could be useful for both plant manufacturers and food industries to develop tailored UV-C LED systems.

Profitability of single- and mixed-culture fermentations for the butyric acid production from a lignocellulosic substrate

Butyric acid (BA) is one of the most promising precursors for pharmaceutical and plastic manufacturers, as well as for fuel butanol production. Lignocellulosic biomass can be used as an adequate source for BA production due to its low prices and widespread abundance. The conversion of lignocellulosic biomass into BA requires different steps depending on the type of inoculum. Pure cultures, which produce high amounts of BA, demand sequential processing of lignocellulosic substrates. In contrast, mixed cultures, which produce a lower amount of BA, work as a consolidated bioprocess, therefore, some processing steps occur simultaneously. It is unknown which of these two schemes for BA production is more profitable yet. The following study presents a review about the most recent advances about BA production from lignocellulose by pure and mixed cultures. In addition, a techno-economic analysis for BA production is considered for each type of inoculum and different plant capacities. The pure strain scheme involves seven stages, while the mixed culture scheme involves only four. Both schemes include the final product purification through membranes where the purity of BA was 99.8%. The mixed culture scheme is more profitable than the pure strain one, with Total Production Costs of 3.2, 1.3, and 0.9 US$/kg for plant capacities of 100, 500, and 1000 ton/day, respectively. With respect to the pure strain scheme, the Total Production Costs are 15.1, 7.3, and 6.5 US$/kg for plant capacities of 100, 500, and 1000 ton/day, respectively. The operating costs in the pure culture plants are 30.4, 81.7, and 145.2 million US$/year for the plant capacities of 100, 500, and 1000 ton/day, respectively. These operating costs are between 1.2 and 1.5 times higher compared with the mixed culture plants. Also, the Total Capital Investment is three times higher with the pure strain scheme.

Impact of temperature, inoculum flow pattern, inoculum type, and their ratio on dry anaerobic digestion for biogas production

This study is aimed to apply dry anaerobic digestion (DAD) for methane (CH4) enriched biogas production from unsorted organic municipal solid waste (MSW). Cumulative biogas production was monitored for 35 days of operation in batch digesters at fixed feedstock to inoculum (F/I) ratio 2. Anaerobic sludge (AS) and cow manure (CM) were used as inoculum in single and mixed modes. Several process parameters such as inoculum flow pattern (single layer, multilayer, and spiral), digestion temperature (25 to 40 °C), inoculation modes (single and mixed mode), and inoculation proportion (AS:CM = 1:1, 1:2, 1:3, and 2:1) were investigated to determine the optimum DAD conditions to maximize the CH4 laden biogas yield. The study of inoculum flow pattern showed that digester with multilayer inoculum configuration generated the maximum 555 mL cumulative biogas with the production rate of 195 mL/day (at 25 °C). Biogas production rate and cumulative biogas production were found to increase with a rise in temperature and the maximum values of 380 mL/day and 1515 mL respectively were observed at 37 °C. The mixed mode of inoculation containing AS and CM augmented the biogas yield at previously optimized conditions. Final results showed that digester with multilayer inoculum flow pattern at 37 °C produced 1850 mL cumulative biogas with 1256.58 mL CH4/kg volatile solid (VS) when the mixed inoculum was used at the AS:CM—1:2 ratio. Biogas production with this significant amount of CH4 justifies the use of the DAD process for energy (biogas) generation from widely available biomass feedstock (MSW), offering various advantages to the environment.

Evaluación del bagazo de Agave salmiana como sustrato para el cultivo de Pleurotus djamor

The objective of this study is to evaluate the potential of agave bagasse supplemented with urea for use as an alternative substrate in the cultivation of a wild fungus isolated from Agave salmiana (A. salmiana), determining the biological efficiency, production rate, morphological characteristics and nutritional. The fungus was identified by molecular methods amplifying the ITS region and subsequently cultivated on A. salmiana bagasse supplemented with urea (0.77, 0.95, 1.14, 1.32 and 1.5% of total nitrogen (TN)). For the cultivation of the fungus, two types of inoculum were used: in the form of grain and in the form of granules. The fungus was identified as Pleurotus djamor. A biological efficiency (BE) of 70% was obtained in the sample inoculated with grain at 1.32% TN, at 1.5% it produced malformations in the fruiting bodies. Chemical analysis of the sporocarps shows a crude protein content of 15-26%. This is the first report of the isolation of P. djamor from A. salmiana as an atypical substrate, which represents an opportunity for its commercialization and the bagasse, due to its chemical composition and being supplemented with urea, allows the growth of the fungus without alter its nutritional composition of this genus.

Changes of nutritional composition of tempeh during fermentation with the addition of Saccharomyces cerevisiae

Abstract. Rizal S, Kustyawati ME, Suharyono AS, Suyarto VA. 2022. Changes of nutritional composition of tempeh during fermentation with the addition of Saccharomyces cerevisiae. Biodiversitas 23: 1553-1559. This study aimed to determine the effect of the addition of Saccharomyces cerevisiae on changes in nutritional composition during tempeh fermentation. The study used a Completely Randomized Block Design with two treatments and two replications. The first treatment was the type of tempeh inoculum with 4 levels, namely 0.2% commercial inoculum (Raprima), 1% Rhizopus oligosporus inoculum, 1% S. cerevisiae inoculum, and a mixture of 1% R. oligosporus inoculum, and 1% S. cerevisiae inoculum. The second treatment was the length of fermentation with 4 levels, namely 0 hours, 15 hours, 30 hours, and 45 hours. Observation parameters include fat, protein, ash, moisture, carbohydrates, and ?-glucan content during fermentation of tempeh. The data obtained were analyzed statistically using the Barlett and Tukey test then continued with the ANOVA test and the Orthogonal Polynomial-Orthogonal Comparison (OP-OC) test at the 5% level. The results showed that the addition of S. cerevisiae as an inoculum in making tempeh had an effect on changes in nutritional content during tempeh fermentation. The fat content, ash content, and moisture content of tempeh increased during fermentation, while the fat content and carbohydrate content decreased. The addition of 1% S. cerevisiae to tempeh fermentation by 1% R. oligosporus at 45 hours of fermentation resulted in the best nutritional content of tempeh with 17.40% protein content, 8.23% fat content, 65.74% moisture content, 1.33 ash content, 7.30% carbohydrate content, and 0.13% ?-glucan content.

In Vitro Assessment of Hydrolysed Collagen Fermentation Using Domestic Cat (Felis catus) Faecal Inocula.

Simple SummaryThe gastrointestinal microbiome of domestic cats can utilise dietary fibre to produce beneficial fermentation end products such as butyrate, an energy source for intestinal cells. However, domestic cats are obligate carnivores and therefore may not require plant derived dietary fibre. It has been hypothesised that in the wild, consumption of animal-derived substrates such as hair and cartilage may be fermented by the cat’s gastrointestinal microbiome, producing butyrate and other beneficial end products. Therefore, the aim of this study was to use a laboratory digestion and fermentation model (simulating the digestion process) to determine the concentrations of butyrate produced by various animal-derived substrates, including hydrolysed collagen, hair, and cartilage. Faecal samples were used in batch cultures to represent the microbes in the cat’s colon. Faecal samples came from cats fed either high protein or high carbohydrate diets. The type of faeces used was found to affect the fermentation profile produced, likely due to differing microbial community compositions, at the start of the batch cultures. Microbes present in high protein faeces fermented the hydrolysed collagen substrate, producing increased concentrations of butyrate. This finding has wider implications for use of animal-derived substrates in species-appropriate diet formulations.The gastrointestinal microbiome has a range of roles in the host, including the production of beneficial fermentation end products such as butyrate, which are typically associated with fermentation of plant fibres. However, domestic cats are obligate carnivores and do not require carbohydrates. It has been hypothesised that in the wild, collagenous parts of prey—the so-called animal-derived fermentable substrates (ADFS) such as tendons and cartilage—may be fermented by the cat’s gastrointestinal microbiome. However, little research has been conducted on ADFS in the domestic cat. Faecal inoculum was obtained from domestic cats either consuming a high carbohydrate (protein:fat:carbohydrate ratio of 35:20:28 (% dry matter basis)) or high protein (protein:fat:carbohydrate ratio of 75:19:1 (% dry matter basis)) diet. ADFS (hydrolysed collagen, cat hair, and cartilage) were used in a series of static in vitro digestions and fermentations. Concentrations of organic acids and ammonia were measured after 24 h of fermentation, and the culture community of microbes was characterised. The type of inoculum used affected the fermentation profile produced by the ADFS. Butyrate concentrations were highest when hydrolysed collagen was fermented with high protein inoculum (p < 0.05). In contrast, butyrate was not detectable when hydrolysed collagen was fermented in high carbohydrate inoculum (p < 0.05). The microbiome of the domestic cat may be able to ferment ADFS to provide beneficial concentrations of butyrate.

Influence of Different Bacteria Inocula and Temperature Levels on the Chemical Composition and Antioxidant Activity of Prickly Pear Vinegar Produced by Surface Culture.

This work intends to determine the effect on the aroma profile, phenolic content and antioxidant activity of prickly pear vinegars produced by the surface culture at two different fermentation temperatures and using different acetic acid bacteria (AAB) inocula. Prickly pear wine was fermented at two temperature levels (30 and 37 °C) by using bacteria inocula containing Acetobacter, Gluconobacter or a mixture of bacteria isolated from Sherry vinegars. Eighty-five individual volatile compounds from different families and sixteen polyphenolic compounds have been identified. It was confirmed that the highest temperature tested (37 °C) resulted in a lower concentration of volatile compounds, while no significant effect on the vinegars’ volatile composition could be associated with the AAB inoculum used. Contrariwise, the highest content of polyphenolic compounds was detected in those vinegars produced at 37 °C and their concentration was also affected by the type of AAB inoculum used. Prickly pear wine displayed greater antioxidant activity than juices or vinegars, while the vinegars obtained through the mixture of AAB from Sherry vinegar showed higher antiradical activity than those obtained through either of the two AAB genera used in this study. It can be therefore concluded that, although the volatile content of vinegars decreased when fermented at a higher temperature, vinegars with a higher content in polyphenols could be obtained by means of partial fermentations at 37 °C, as long as thermotolerant bacteria were employed.

The effect of pH, temperature, and inoculum on the fermentation of pulp and paper biosludge: increasing the nutrient availability for rearing of black soldier fly larvae

Pulp and paper production is one of the largest global industries producing annually 400 million metric tons of pulp and paper products and 6 million tons of pulp and paper biosludge (PPBS). From a resource efficiency and sustainability perspective, there is a need for improving PPBS management. This study assessed fermentation of PPBS as pretreatment to improve PPBS feasibility as feed for black soldier fly larvae. The impact of temperature, pH, and inoculum on the concentration of soluble chemical oxygen demand (sCOD) and volatile fatty acids (VFA) was assessed. An initial pH of 10 and the addition of inoculum from an anaerobic digester substantially increased the concentration of sCOD. The obtained concentration of VFA was low compared to the VFA concentration needed to improve the growth of Black Soldier Fly Larvae (BSFL). The PPBS is recalcitrant to fermentation because of the high content of lignocellulose. Fermentation as done in this study does not convert PPBS to a feasible feed for black soldier fly larvae; thus, further research on improved fermentation is needed. However, fermentation at alkaline pH and addition of inoculum do increase the final pH of PPBS which improves its feasibility as feed for BSFL. Future studies should explore pH > 10 and temperatures > 55 °C to increase sCOD and improving generation of VFA by removal of inhibiting substances, testing other types of inoculum (rumen microorganisms) and co-fermentation.

Kinetic Study on the Effect of Substrate and Micronutrient Inhibition during Anaerobic Fermentation of Biohydrogen

There are several factors that influence the production of biohydrogen by dark fermentation including inoculum seeds, type and concentration of substrate, pH, temperature, presence of micronutrient and reactor configuration. Previous research has proven that the concentration of substrate and the presence of micronutrient will influence the yield and productivity of biohydrogen production. However, improvement of yield and productivity of the process can only be achieved once the system is under the optimum amount of substrate and micronutrient. Therefore, the best way to determine the effect of substrate concentration and presence of micronutrient is through kinetic study that was done using Monod model along with Andrews model. Besides that, the substrate inhibition effect also will be evaluated to determine the maximum substrate that needs to be supplied for maximum hydrogen production, and thus supplied the information for economic feasibility for fermentation process. In the meantime, the inhibition effect of adding the iron nanoparticles also had been evaluated in order to understand the interaction effect between iron nanoparticles and bacteria in term of catabolism reaction. It was found that increasing the substrate concentration more than 10 g/l will cause the inhibition to the system, in which it will slow down the reaction process and reduced the production of hydrogen. While the presence of iron NPs more than its optimum value (200 mg/l) will inhibit the bacterial growth and hence, affect the hydrogen production. For both cases, when the inhibition occurred at the respective concentration, it was found that the metabolic pathway was shifted to produce more hydrogen-consuming metabolite such as propionate acid, and thus, dropped the hydrogen production.