Physicochemical, Sensory, and Microbial Characteristics of Kindirmou and Pendidam, Two Traditional Fermented Milks of Adamawa - Cameroon, as Affected by the Fermentation Vessels

Recent data show that the containers traditionally used for fermentation, due to their nature, exchange with the fermented product, the consequence being a modification of the physico-chemical, microbiological and organoleptic properties of these products. The objective of this work is to study the influence of the fermentation vessel on the sensory, physicochemical, and microbial properties of kindirmou and pendidam, two traditional fermented milks from Adamawa - Cameroon. To this end, a descriptive test was used to generate the sensory properties of fermented milks in different containers, followed by biochemical (pH, titratable acidity, protein, sugar content, and total phenolic compounds) and microbiological analyses (total aerobic mesophilic flora, coliforms, lactic acid bacteria, yeasts and molds). Regarding sensory evaluation, samples of kindirmou and pendidam fermented in calabashes have a higher general acceptability than those fermented in plastic buckets and enamel plates. The total mesophilic flora and total coliforms were higher than the norm (≥ 6log10) for kindirmou and pendidam regardless of the fermentation vessel. The absence of yeasts and molds is noted in the samples of kindirmou, while they are found at very high levels in the samples of pendidam fermented in the calabash and in the enamel plates ((≥ 6log10). Fecal coliforms are absent in samples of kindirmou and pendidam fermented in the calabash, while they are found in samples fermented in plastic buckets and enamel plates. On the physicochemical level, the results obtained showed that the kindirmou fermented in the calabash had the highest soluble protein content (1.47 ± 0.04 g / 100 mL of milk) than those fermented in plastic bucket and enamel plates. The phenolic compounds are present only in the samples of milk fermented in the calabash and the average contents are 93.41 ± 3.04 mg / 100 mL of milk for kindirmou and 111.20 ± 2.01 mg / 100 mL for pendidam. To conclude, kindirmou and pendidam fermented in calabashes exhibit the best sensory and physicochemical characteristics, and are rich in bioactive compounds than those fermented in plastic buckets and enamel plates.

One-pot production of butyl butyrate from glucose using a cognate “diamond-shaped” E. coli consortium

Esters are widely used in plastics, textile fibers, and general petrochemicals. Usually, esters are produced via chemical synthesis or enzymatic processes from the corresponding alcohols and acids. However, the fermentative production of esters from alcohols and/or acids has recently also become feasible. Here we report a cognate microbial consortium capable of producing butyl butyrate. This microbial consortium consists of two engineered butyrate- and butanol-producing E. coli strains with nearly identical genetic background. The pathways for the synthesis of butyrate and butanol from butyryl-CoA in the respective E. coli strains, together with a lipase-catalyzed esterification reaction, created a “diamond-shaped” consortium. The concentration of butyrate and butanol in the fermentation vessel could be altered by adjusting the inoculation ratios of each E. coli strain in the consortium. After optimization, the consortium produced 7.2 g/L butyl butyrate with a yield of 0.12 g/g glucose without the exogenous addition of butanol or butyrate. To our best knowledge, this is the highest titer and yield of butyl butyrate produced by E. coli reported to date. This study thus provides a new way for the biotechnological production of esters.

One-pot production of butyl butyrate from glucose using a cognate “diamond-shaped” E. coli consortium

Esters are widely used in plastics, textile fibers, and general petrochemicals. Usually, esters are produced via chemical synthesis or enzymatic processes from the corresponding alcohols and acids. However, the fermentative production of esters from alcohols and/or acids has recently also become feasible. Here we report a cognate microbial consortium capable of producing butyl butyrate. This microbial consortium consists of two engineered butyrate- and butanol-producing E. coli strains with nearly identical genetic background. The pathways for the synthesis of butyrate and butanol from butyryl-CoA in the respective E. coli strains, together with a lipase-catalyzed esterification reaction, created a “diamond-shaped” consortium. The concentration of butyrate and butanol in the fermentation vessel could be altered by adjusting the inoculation ratios of each E. coli strain in the consortium. After optimization, the consortium produced 7.2 g/L butyl butyrate with a yield of 0.12 g/g glucose without the exogenous addition of butanol or butyrate. To our best knowledge, this is the highest titer and yield of butyl butyrate produced by E. coli reported to date. This study thus provides a new way for the biotechnological production of esters.

PERBAIKAN PROSES FERMENTASI BIJI KAKAO KERING DENGAN PENAMBAHAN TETES TEBU, KHAMIR, DAN BAKTERI ASAM ASETAT

Most of cocoa beans produced by smallholder farmers were non fermented which can be improved by modifiedfermentation processing. This study was aimed to inverstigate the influence of molasses, yeast Saccharomycescerevisiae, and Acetobacter aceti addition on dried cocoa beans fermentation process.Fresh cocoa beans were dried in a glasshouse and its reducing sugar was analyzed before and after drying. Asmall plastic bucket (20 cm diameter and 30 cm height) with aeration holes was used as fermentation vessel. Driedcocoa beans were soaked in distilled water for 4 hours, inoculated with yeast and acetic acid bacteria cultures, andmolasses were added at two different concentration, i.e, 1 and 1.5 times of reducing sugar lost during drying.Reducing sugar, ethanol, titrated acid, population of yeast, and acetic acid bacteria were monitored duringfermentation. After fermentation the beans were sun dried and its pH and degree of fermentation were determinedto assess the bean quality.The results showed that the addition of molasses mostly at the level of 1.5, S. cerevisiae, and A. aceti increasereducing sugar, ethanol, titrated acid, yeast and acetic acid bacteria of fermentation liquid (pulp). The highestpercentage of fermented beans (68.4 %) was achieved by addition of S. cerevisiae, A. aceti, and molasses atthe level 1.5. It is likely that the addition of S. cerevisiae, A. aceti, and molasses could improve fermentationprocessing of dried cocoa bean.

Effect of microbial oil, evening primrose oil and borage oil on rumen fermentation in vitro

The objective of this study was to examine the effects of microbial oil, evening primrose oil and borage oil on rumen fermentation of a diet consisting of 80% of hay and 20% of barley in an artificial rumen (Rusitec). All three oils contained gamma-linolenic acid (GLA), microbial oil – 8.4%, evening primrose oil – 9.2% and borage oil – 23.7% out of the total fatty acid content. The experiment in Rusitec lasted 11 days. After a stabilization period (5 days), microbial oil (5% wt/wt) was added into fermentation vessel V₂, evening primrose oil (5% wt/wt) into V₃ and borage oil (5%wt/wt) into V₄ (6 days). Fermentation vessel V₁ served as a control (without oils). The results showed that the oils did not affect any of the basal parameters of rumen fermentation (pH, NH₃-N, degradation of dry matter, organic matter, neutral detergent fibre, acid detergent fibre). Methane production (mmol/day) was reduced numerically by the oils; microbial oil, evening primrose oil and borage oil decreased CH₄ production about 11.32%, 11.45% and 2.04%, respectively. The supplementation of the oils to the total mixed ration (TMR) significantly decreased percentage proportions of short-chain fatty acids (SCFA, about 0.1–0.3%), medium-chain fatty acids (MCFA, about 8%) and increased long-chain fatty acids (LCFA, about 8%) in the effluent. Stearic acid C_18:0 was the major FA in the effluent and was significantly reduced in oil supplemented diets. The percentage proportion of trans C_18:1 isomers significantly increased (1.7–2 times) in all oil supplemented diets. The main intermediates – cis 9, trans 11 C_18:2 (CLA) and trans 11 C_18:1(TVA) also increased after oil supplementation of the diet. TVA concentration with microbial oil, evening primrose oil and borage oil supplementation was 3.17%, 8.19% and 9.3% in comparison with the control (1.38%). CLA concentration significantly increased 2.3, 1.2, and 2.1 times after microbial oil, evening primrose oil and borage oil supplementation in Rusitec. Finally, the oil supplementation caused incomplete biohydrogenation of unsaturated FA and it was characterized by an increase in TVA concentration and TVA to C_18:0 ratio in oil supplemented diets.

Effect of microbial oil, monensin and fumarate on rumen fermentation in artificial rumen

The objective of this study was to investigate the effect of microbial oil on rumen fermentation of a diet composed of 60% hay and 40% barley in an artificial rumen (Rusitec). Microbial oil (MO) was produced by the fungus Thamnidium elegans. This fungus grew on the wheat bran/spent malt grains (3:1) mixture. The fatty acid composition of microbial oil was as follows: 0.7% C_14:0, 15.4% C_16:0, 10.1% C_18:0, 50.9% C_18:1, 13.9% C_18:2 and 8.4% C_18:3 (GLA, γ-linolenic acid). The effect of monensin MON (66 ppm) and fumarate FUM (6.25 mmol) with and without MO supplementation was also studied. The experiment in Rusitec lasted 11 days. After a stabilization period (5 days), MO was added to fermentation vessel V₂ (6 days), MON to fermentation vessel V₃ (6 days) and FUM to fermentation vessel V₄(6 days). MO was also added to V₃ and V₄ on the last day together with MON (V₃) and FUM (V₄). The fermentation vessel V₁served as control (without additives). The results showed that MO reduced (P < 0.05) mol% acetate and increased (P < 0.05) mol% propionate and n-butyrate. Methane production (mmol/day) was reduced numerically (NS). The efficiency of microbial synthesis (EMS) was also reduced numerically and nitrogen incorporated by the microflora (N_M) was reduced significantly in MO supplementation. There were no differences in the rumen fermentation when MO was applied together with MON and FUM compared to the vessel where only MO was applied. No additive effect was observed in the relationship MO-ionophore or MO-FUM. Monensin and fumarate applied separately showed their typical effects on rumen fermentation in vitro.