Section 133. Parole permits may be granted by the parole board to prisoners subject to its jurisdiction at such time as the board in each case may determine; provided, however, that no prisoner sentenced to the state prison shall be eligible for such permit until such prisoner shall have served the minimum term of sentence, pursuant to section twenty-four of chapter two hundred and seventy-nine, as such minimum term of sentence may be reduced by deductions allowed under section one hundred and twenty-nine D. Where an inmate is serving two or more consecutive or concurrent state prison sentences, a single parole eligibility shall be established for all such sentences. Prisoners who are granted parole permits shall remain subject to the jurisdiction of the board until the expiration of the maximum term of sentence or, if a prisoner has two or more sentences to be served otherwise than concurrently, until the aggregate maximum term of such sentence, unless earlier terminated by the board under the provisions of section one hundred thirty A. Sentences of imprisonment in the state prison shall not be suspended in whole or in part.