Enhancing Hydrogen Productivity of Photosynthetic Bacteria from the Formulated Carbon Components of Lignocellulose

doi:10.21203/rs.3.rs-708580/v1

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Enhancing Hydrogen Productivity of Photosynthetic Bacteria from the Formulated Carbon Components of Lignocellulose

https://doi.org/10.21203/rs.3.rs-708580/v1

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To develop an efficient photofermentative process capable of higher rate biohydrogen production using carbon components of lignocellulosic hydrolysate, a desired carbon substrate by mixing xylose with glucose was formulated. Effects of crucial process parameters affecting cellular biochemical reaction of hydrogen by photosynthetic bacteria (PSB), i.e variation in initial concentration of total carbon, glucose content in initial carbon substrate, as well as light intensity were experimental investigated using response surface methodology (RSM) with a Box-Benhnken design (BBD). Hydrogen production rate (HPR) in the maximum value of 30.6 mL h^− 1 L^− 1 was attained under conditions of 39 mM initial concentration of total carbon, 59% (mol/mol) glucose content in initial carbon substrate and 12.6 W m^− 2 light intensity at light wavelength of 590 nm. Synergic effects of metabolizing such a well formulated carbon substrate for sustaining the active microbial synthesis to sufficiently accumulate biomass in bioreactor, as well as stimulating enzyme activity of nitrogenase for the higher rate biohydrogen production were attributed to this carbon substrate can enable PSB to maintain the relatively consistent microenvironment in suitable culture pH condition during the optimized photofermentative process.

General Biochemistry

Biotechnology and Bioengineering

Photofermentative hydrogen production

lignocellulose

photosynthetic bacterial growth

nitrogenase activity

response surface methodology (RSM)

Table 1 Symbols and intervals used in Box-Behnken design (BBD)

Independent variable	Symbol	Intervals
Independent variable	Symbol	-1	0	1
C_i (Initial substrate concentration)	x₁ (mM)	20	35	50
A (Glucose content in initial substrate)	x₂ (%mol/mol)	0	50	100
I (Light intensity)	x₃ (W/m²)	5.8	11.6	17.4

Table 2 Experiment design and results for HPR(mL/L/h)

Runs	x₁ (mM)	x₂ (%mol/mol)	x₃ (W m^-2)	HPR (mL h^-1L^-1)
1	20	50	17.4	21.8±0.2
2	35	0	5.8	20.4±0.2
3	20	100	11.6	23.2±0.1
4	50	0	11.6	23.0±0.3
5	50	50	17.4	27.0±0.2
6	35	50	11.6	29.5±0.1
7	35	0	17.4	20.2±0.3
8	35	100	17.4	24.9±0.3
9	50	50	5.8	23.2±0.1
10	20	0	11.6	18.9±0.2
11	50	100	11.6	23.9±0.3
12	20	50	5.8	21.8±0.2
13	35	100	5.8	22.9±0.4
14	35	50	11.6	29.9±0.3
15	35	50	11.6	29.7±0.1
^aExperimental results are averages (±standard deviation) of the values obtained in independent experiments conducted in triplicate (N=3)

Table 3 ANOVA for dependent variables: H₂ production rate (HPR)

Factors	Sum of squares	Degree freedom	Mean square	F-value	P-value
Model	177.04	9	19.67	53.70	0.0002
x₁	13.52	1	13.52	36.91	0.0017
x₂	19.22	1	19.22	52.47	0.0008
x₃	5.44	1	5.44	14.86	0.0119
x₁x₂	2.89	1	2.89	7.89	0.0376
x₁x₃	5.76	1	5.76	15.72	0.0107
x₂x₃	1.21	1	1.21	3.30	0.1288
x₁²	38.01	1	38.01	103.75	0.0002
x₂²	68.54	1	68.54	187.09	<0.0001
x₃²	41.64	1	41.64	113.68	0.0001
Residual	1.83	5	0.37
Lack of fit	1.71	3	0.57	8.97	0.1019
Pure Error	0.13	2	0.063
Cor Toal	178.87	14
R-squared	0.9898	Adj-squared	0.9713
Pred R-squae	0.8459	Adeq Precision	22.697
C.V.%	2.53

Table 4 Comparison of studies on growth kinetics of PSB using logistic model

Strains	Substrate	Operation mode	x₀ (g L^-1)	x_max (g L^-1)	k_c (h^-1)	R²	Ref.
R.sphaeroides O.U. 001	Malic acid	Batch	0.041	1.02	0.103	0.98	[20]
R.sphaeroides O.U. 001	Olive mill wastewater	Batch	0.062	0.552	0.087	0.99	[26]
R.sphaeroides O.U. 001	Olive mill wastewater	Batch	0.067	0.565	0.109	0.99	[27]
R.capsulatus MT1131	Acetic acid	Continuous	0.53	1.61	0.1	0.92	[28]
Rhodobacter Capsulatus	DL-lactate	Batch	---	0.835	0.39	0.98	[29]
Rhodobacter Capsulatus	Malate	Batch	---	0.93	0.17	0.97	[30]
R.sphaeroides O.U. 001	Malate, Lactate , Acetate	Continuous	0.07	0.63	0.18	0.98	[31]
R.sphaeroides O.U. 001	Malate	Continuous	0.11	0.71	0.069	0.98	[32]
R. capsulatus	Lactic acid Acetic acid	Batch	0.09	1.09	0.04	0.99	[21]
R. faecalis RLD-53	Acetate	Batch	---	0.83	0.062	0.98	[22]
R.palustris DSM 123	DL malic acid	Continuous		1.35	0.052	0.97	[33]
R.palustris	Glucose Xylose	Batch	0.03	0.976	0.176	0.99	This study

Table 5 Comparison of studies on experimental optimization of photofermentative H₂ production

Strains	Substrate	Operation/cell state	Design method	HPR (mL h^-1 L^-1)	Ref.
Mixed consortium	Acetate, Propionate, Butyrate	Batch/suspended	BBD	12.5	[34]
R. capsulatus DSM 1710	Acetic acid, lactic acid	Batch/suspended	3^k	12.6	[35]
Rhodobacter sp. KKU-PS1	Malic acid	Continuous/immobilized	CCD	12.0	[36]
Mixed consortium	Corn stalk	Continuous/immobilized	---	38.4	[37]
Rhodobacter sphaeroides DSM 158	DL malic acid	Batch/suspended	BBD	41.7	[38]
R.palustris CQK 01	Glucose	Batch/suspended	---	12.09	[39]
R.palustris DSM 123	DL malic acid	Continuous/immobilized	3^k	6.885	[33]
R. capsulatus DSM 1710	Acetate	Batch/suspended	BBD	21	[40]
R. Palustris WP3-5	Butyric acid	Batch/suspended	CCD	12.3	[41]
R. palustris	Glucose Xylose	Batch/suspended	BBD	30.6	This study

CCD – central composite design

3^k – three-level general full factorial design

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Reviews received at journal
14 Jul, 2021
Reviewers invited by journal
13 Jul, 2021
Editor invited by journal
12 Jul, 2021
First submitted to journal
11 Jul, 2021

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Enhancing Hydrogen Productivity of Photosynthetic Bacteria from the Formulated Carbon Components of Lignocellulose

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